I just did several upgrades & migrations... 2 x stretch->buster->bullseye last week, then 2 x bullseye->chimaera :
I saw the same problem after

apt-get install eudev

init and sysvinit-core removed just before rebooting without init ...

As my wheezy NAS was systemd-free, no problem there after wheezy->jessie, direct migration to beowulf,
and beowulf->chimaera, a piece of cake

I'm fairly new to all this. My apologies if this is the wrong place to post.

I just did my first Bullseye -> Chimaera migration. It went a little rough (I had not found this post until after, lol) but I was able to finally get it going by installing "sysvinit-core" from Recovery Mode. It seems apt-get install sysvinit-core may be missing from the official instructions here: https://www.devuan.org/os/documentation … o-chimaera . Is that step intentionally missing?

Basically:

1. Eudev install fails as DPKG tries to remove systemd with no alternate Init present. (probably expected behavior)
2. apt install -f doesn't have anything to fix.
3. Then I did reboot per instructions; hilarity ensued. (Half working system, Systemd spraying failed service message all over the console, keyboard keys randomly not working, etc. It's amazing it booted at all!)
4. Performed apt install sysvinit-core from Recovery Mode.
5. I then was able to install eudev from Recovery Mode and did dist-upgrade. (not sure if rebooted in between 4 and 5 or just after step 5)

EDIT: Typos; added clarity.

Supported DE’s:

   GNOME/GNOME FLASHBACK
    LXDE
    LXQT
    XFCE
    KDE
   MATE
   CINNAMON

also SERVER migration is possible but risky
if you are not sitting in the same room with the server.

This script is tested only in virtualbox as I don't have
machines to migrate right now.
Backwards compatibility for buster to beowulf should
work but is untested.

I hope there are some fearless testers!

Hints, improvements and critics are welcome.

So I tried slim:
- installed slim, and packagekit. 
- uninstalled lightdm
Luck!  It worked with slim, after I installed both slim and packagekit.

I never could get lightdm to work, yet.  I guess that possibly my *kits were not in order.   At any rate the migration was successful.

I hope this helps.

Awesome!!!

FSR > This is the short version (explanation) of what I have been able to do with consistent results.  The final result is I had to remove lightdm and install slim.   A login with lightdm killed the lightdm service. 

# this is a personal choice to view network connection and its info:
apt install net-tools

apt install sysvinit-core

change apt sources.list to chimaera

added /etc/default/su

apt install devuan-keyring    ( with wget and dpkg -i )

log out of root terminal to exit, then su to root again to load PATH

apt update

# This is just to get the packages in cache in case network connection is lost
# They throw up errors with systemd installed
apt install eudev network-manager lightdm --download-only

reboot  ( and keep your fingers crossed )

apt install eudev

apt install network-manager lightdm

apt remove libnss-systemd systemd systemd-timesyncd dbus-user-session --purge

apt install task-xfce-desktop

apt dist-upgrade

reboot

Final status:  I had a very hard time getting a login to an X session to work.  I was not successful with lightdm and this is what I tried: 
- reinstalled lightdm
- ran "lightdm --test-mode --debug" and I saw an error about missing Xephyr, so I installed xserver-xephyr and the error went away, but still it is not working.  When I enter the username and password on the login screen, it kills lightdm.
- nothing noted in any other log files
- installing all removed files from earlier in the migration, especially with the first apt install of sysvinit-core, less any obvious sysd packages

So I tried slim:
- installed slim, and packagekit. 
- uninstalled lightdm
Luck!  It worked with slim, after I installed both slim and packagekit.

I never could get lightdm to work, yet.  I guess that possibly my *kits were not in order.   At any rate the migration was successful.

I hope this helps.

Edit:  Yes it will break something important.  After an "apt autoremove" of these packages, I no longer get an x login screen with lightdm.  Lightdm does not start with the boot, but it will with a "service lightdm restart" (or start).  However, with lightdm started with the command all options on the xfce logout menu are greyed out and not functioning.  Also, reinstalling these programs with apt install... does not fix the broken login.  Lightdm still will only start manually. 

I am about to do this migration again, from the beginning, and I will copy all text output from the commands.  It will be lengthy and thus not posted here.  If you want it, let me know.

Just my two cents, in case it's useful - I had a similar problem with slim after removing most desktop defaults from a Bullseye-based antiX beta a couple of days ago. In order to move past the problem and continue hacking on antiX without having to figure out the broken login manager right away, I purged slim and installed tbsm, a desktop login manager for tty. Works great out of the box, and I also then tested it on Devuan Chimaera which seemed quite happy with it. Good luck!

The following packages were automatically installed and are no longer required:
  colord-data fonts-quicksand gnome-desktop3-data libappstream4 libcolorhug2
  libglib2.0-bin libgnome-desktop-3-19 libgusb2 libpipewire-0.3-0
  libpipewire-0.3-modules libplymouth5 libspa-0.2-modules libstemmer0d
  libxkbregistry0 libyaml-0-2 openntpd pipewire pipewire-bin usb.ids
  xdg-desktop-portal

Would an apt autoremove now break anything important?

Edit:  Yes it will break something important.  After an "apt autoremove" of these packages, I no longer get an x login screen with lightdm.  Lightdm does not start with the boot, but it will with a "service lightdm restart" (or start).  However, with lightdm started with the command all options on the xfce logout menu are greyed out and not functioning.  Also, reinstalling these programs with apt install... does not fix the broken login.  Lightdm still will only start manually. 

I am about to do this migration again, from the beginning, and I will copy all text output from the commands.  It will be lengthy and thus not posted here.  If you want it, let me know.

libreoffice should have been taken off the autoremove list along with other things when you installed task-xfce-desktop. You're sure it's still there and didn't get removed again behind your back?

FSR, I have been gone for the past few days and I unplugged while away.  I gave this a spin this morning and this is what I did.  This is my feeble attempt to add to your documentation.  The migration from bullseye on the netiso file was pretty straightforward, while the migration with xfce was a little more complicated with eudev causing the network connection problem.  Please pardon me for the long post as I will include some notation for clarity.  This is not a guide.  It is more notes than anything.

Steps for bullseye to chimaera migration:

Installed debian from:
   

and select only system utilities and ssh server.

Install net-tools, to see ip address info
   

   
Install sysvinit-core
   

apt install sysvinit-core

   
Need to alter or add PATH  to use "dpkg -i"

Added to /etc/default/su
    ALWAYS_SET_PATH yes

*** Reboot to load sysvinit ****

Download keyring
   

wget wget http://pkgmaster.devuan.org/devuan/pool/main/d/devuan-keyring/devuan-keyring_2017.10.03_all.deb

   
Then installed keyring
   

dpkg -i devuan-keyring_2017.10.03_all.deb

changed sources in /etc/apt/sources.list
# CHIMAERA
deb http://deb.devuan.org/merged/ chimaera main contrib non-free
deb http://deb.devuan.org/merged/ chimaera-updates main contrib non-free
deb http://deb.devuan.org/merged chimaera-proposed-updates main non-free contrib
#deb http://deb.devuan.org/merged/ chimaera-security main contrib non-free
#deb http://deb.devuan.org/merged/ chimaera-backports main contrib non-free

apt update

&

apt dist-upgrade

root@localhost:/home/guest# apt dist-upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages will be REMOVED:
  libnss-systemd systemd systemd-timesyncd
The following NEW packages will be installed:
  eudev libeudev1
The following packages will be upgraded:
  apt apt-utils base-files bsdextrautils bsdutils dbus distro-info-data eject
  fdisk init init-system-helpers initscripts libapt-pkg6.0 libblkid1
  libdbus-1-3 libfdisk1 libmount1 libprocps8 libsmartcols1 libudev1 libuuid1
  mount net-tools procps python3-reportbug reportbug rsyslog sysv-rc
  sysvinit-core sysvinit-utils task-english task-ssh-server tasksel
  tasksel-data udev util-linux util-linux-locales
37 upgraded, 2 newly installed, 3 to remove and 0 not upgraded.
Need to get 11.0 MB of archives.
After this operation, 18.0 MB disk space will be freed.
Do you want to continue? [Y/n] y

No sysd here:
   

    root@localhost:/home/guest#

Now, the migration using the same debian netiso disk with the Desktop Environment, XFCE, SSH, and Standard System Utilities is slightly more complicated because of getting eudev installed - with a working internet connection.  What I did was to install it after the connection was down, but the .deb files had already been downloaded to /var/cache/apt/archives .  Not a clean way of doing this, I admit, but it did work and maybe you or someone else can perfect and simplify this procedure.  This is what I did.

root@localhost:/home/guest# apt install sysvinit-core
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages were automatically installed and are no longer required:
... text removed ...
Use 'apt autoremove' to remove them.
The following additional packages will be installed:
  dbus-x11 initscripts insserv orphan-sysvinit-scripts psmisc startpar sysv-rc
Suggested packages:
  bootchart2 bootlogd
The following packages will be REMOVED:
  colord dbus-user-session libpam-systemd light-locker lightdm modemmanager
  network-manager network-manager-gnome packagekit packagekit-tools
  policykit-1 policykit-1-gnome rtkit synaptic systemd-sysv task-xfce-desktop
  xdg-desktop-portal-gtk xiccd
The following NEW packages will be installed:
  dbus-x11 initscripts insserv orphan-sysvinit-scripts psmisc startpar sysv-rc
  sysvinit-core
0 upgraded, 8 newly installed, 18 to remove and 0 not upgraded.
Need to get 660 kB of archives.
After this operation, 40.4 MB disk space will be freed.
Do you want to continue? [Y/n]
 
added /etc/default/su to set PATH

installed from devuan what was removed above from debian:
root@localhost:/etc/apt# apt install lightdm modemmanager network-manager network-manager-gnome synaptic rtkit task-xfce-desktop xdg-desktop-portal-gtk xiccd
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libappstream4 libglib2.0-bin libplymouth5 libstemmer0d libyaml-0-2
Use 'apt autoremove' to remove them.
The following additional packages will be installed:
  colord elogind eudev gir1.2-polkit-1.0 libelogind0 libeudev1 libnm0
  libpam-elogind libpolkit-agent-1-0 libpolkit-gobject-1-0
  libpolkit-gobject-elogind-1-0 libudev1 policykit-1 policykit-1-gnome
  task-desktop task-english task-ssh-server tasksel tasksel-data udev
Suggested packages:
  accountsservice xserver-xephyr libteam-utils
  network-manager-openconnect-gnome network-manager-openvpn-gnome
  network-manager-vpnc-gnome network-manager-pptp-gnome dwww menu deborphan
  apt-xapian-index software-properties-gtk evince
The following packages will be REMOVED:
  libnss-systemd libsystemd0 plymouth plymouth-label systemd systemd-timesyncd
The following NEW packages will be installed:
  colord elogind eudev libelogind0 libeudev1 libpam-elogind
  libpolkit-gobject-elogind-1-0 lightdm modemmanager network-manager
  network-manager-gnome policykit-1 policykit-1-gnome rtkit synaptic
  task-xfce-desktop xdg-desktop-portal-gtk xiccd
The following packages will be upgraded:
  gir1.2-polkit-1.0 libnm0 libpolkit-agent-1-0 libpolkit-gobject-1-0 libudev1
  task-desktop task-english task-ssh-server tasksel tasksel-data udev
11 upgraded, 18 newly installed, 6 to remove and 43 not upgraded.
Need to get 11.5 MB of archives.
After this operation, 21.4 MB of additional disk space will be used.
Do you want to continue? [Y/n]

had a problem with openntpd, fixed with
   

apt -f install

It finished.

apt update

apt dist-upgrade

root@localhost:/etc/apt# apt dist-upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
... text removed ...
Use 'apt autoremove' to remove them.
The following packages will be REMOVED:
  libsystemd0 systemd
The following NEW packages will be installed:
  clearlooks-phenix-deepsea-theme deepsea-icon-theme dmz-cursor-theme elogind
  eudev gnome-extra-icons gnome-icon-theme gtk2-engines
  gtk3-nooverlayscrollbar libelogind0 libeudev1 libjpeg-turbo-progs
  libpam-elogind libpolkit-gobject-elogind-1-0 libturbojpeg0 policykit-1
  policykit-1-gnome xscreensaver xscreensaver-data
The following packages will be upgraded:
  apt apt-utils base-files bsdextrautils bsdutils colord-data dbus dbus-x11
  desktop-base distro-info-data eject fdisk gir1.2-packagekitglib-1.0
  gir1.2-polkit-1.0 init init-system-helpers initscripts libapt-pkg6.0
  libblkid1 libcolord2 libcolorhug2 libdbus-1-3 libfdisk1
  liblightdm-gobject-1-0 libmount1 libnm0 libpackagekit-glib2-18 libpcsclite1
  libpolkit-agent-1-0 libpolkit-gobject-1-0 libprocps8 libsmartcols1 libudev1
  libudisks2-0 libuuid1 mount net-tools procps python3-reportbug reportbug
  rsyslog sysv-rc sysvinit-core sysvinit-utils task-desktop task-english
  task-ssh-server tasksel tasksel-data udev udisks2 util-linux
  util-linux-locales xfce4-session
54 upgraded, 19 newly installed, 2 to remove and 0 not upgraded.
Need to get 39.5 MB/42.7 MB of archives.
After this operation, 29.4 MB of additional disk space will be used.
Do you want to continue? [Y/n]

had errors, "apt -f install" did not fix, so I rebooted.

reboot

Have not figured how to bring up eth0

apt install eudev

    // was previously downloaded but not installed

service networking restart

     // gets an ip address from dhcp, continuing with the dist-upgrade

apt remove libnss-systemd systemd systemd-timesyncd dbus-user-session --purge

No sysd here:
   

dpkg -l | grep systemd

returns nothing

What should be done with these?  I assume they are leftovers from a removed meta package from debian.  Which ones should be manually installed for a full working desktop?  Some of these, like LibreOffice I know should be manually installed.  I am at a loss here.  It is a lot of programs orphaned from a meta package, if this is the case.

root@localhost:/home/guest# apt dist-upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
  acl coinor-libcbc3 coinor-libcgl1 coinor-libclp1 coinor-libcoinmp1v5
  coinor-libcoinutils3v5 coinor-libosi1v5 colord-data cups-client
  cups-pk-helper dns-root-data dnsmasq-base espeak-ng-data exfalso
  fonts-font-awesome fonts-lato fonts-opensymbol fonts-quicksand gimp-data
  gir1.2-atspi-2.0 gir1.2-gst-plugins-base-1.0 gir1.2-gstreamer-1.0
  gir1.2-gtksource-3.0 gir1.2-javascriptcoregtk-4.0 gir1.2-keybinder-3.0
  gir1.2-notify-0.7 gir1.2-packagekitglib-1.0 gir1.2-polkit-1.0
  gir1.2-secret-1 gir1.2-soup-2.4 gir1.2-webkit2-4.0 gir1.2-wnck-3.0
  gnome-accessibility-themes gnome-desktop3-data gnome-keyring
  gnome-keyring-pkcs11 gnome-themes-extra gnome-themes-extra-data
  gstreamer1.0-gtk3 gstreamer1.0-pulseaudio gtk2-engines-pixbuf hyphen-en-us
  ipp-usb iptables javascript-common libabw-0.1-1 libamd2 libao-common libao4
  libappstream4 libatk-adaptor libaudio2 libayatana-appindicator3-1
  libayatana-ido3-0.4-0 libayatana-indicator3-7 libbabl-0.1-0 libbluetooth3
  libboost-filesystem1.74.0 libboost-iostreams1.74.0 libboost-locale1.74.0
  libboost-thread1.74.0 libbrlapi0.8 libcamd2 libccolamd2 libcdr-0.1-1
  libcholmod3 libclucene-contribs1v5 libclucene-core1v5 libcmis-0.5-5v5
  libcolamd2 libcolorhug2 libcurl4 libdotconf0 libe-book-0.1-1 libeot0
  libept1.6.0 libepubgen-0.1-1 libespeak-ng1 libetonyek-0.1-1 libexiv2-27
  libexttextcat-2.0-0 libexttextcat-data libfreehand-0.1-1 libgd3
  libgegl-0.4-0 libgegl-common libgexiv2-2 libgimp2.0 libglib2.0-bin
  libgnome-desktop-3-19 libgpgmepp6 libgphoto2-6 libgphoto2-l10n
  libgphoto2-port12 libgusb2 libieee1284-3 libip6tc2 libjim0.79 libjs-jquery
  libjs-sphinxdoc libjs-underscore libjuh-java libjurt-java liblangtag-common
  liblangtag1 libldb2 liblibreoffice-java liblightdm-gobject-1-0 liblouis-data
  liblouis20 libmbim-glib4 libmbim-proxy libmetis5 libmhash2 libmm-glib0
  libmspub-0.1-1 libmwaw-0.3-3 libmythes-1.2-0 libndp0 libneon27-gnutls
  libnetfilter-conntrack3 libnfnetlink0 libnl-route-3-200 libnm0 libnma-common
  libnma0 libnumbertext-1.0-0 libnumbertext-data libodfgen-0.1-1
  liborcus-0.16-0 liborcus-parser-0.16-0 libpackagekit-glib2-18
  libpagemaker-0.0-0 libpam-gnome-keyring libpcaudio0 libpcsclite1
  libpipewire-0.3-0 libpipewire-0.3-modules libplymouth5 libpython3.9
  libqmi-glib5 libqmi-proxy libqrcodegencpp1 libqxp-0.0-0 libraptor2-0
  librasqal3 libraw20 librdf0 libreoffice-base-core libreoffice-calc
  libreoffice-common libreoffice-core libreoffice-draw libreoffice-gtk3
  libreoffice-help-common libreoffice-help-en-us libreoffice-impress
  libreoffice-math libreoffice-style-colibre libreoffice-writer
  librevenge-0.0-0 libridl-java libsane-common libsane1 libsmbclient
  libsnmp-base libsnmp40 libsonic0 libspa-0.2-modules libspeechd2
  libstaroffice-0.0-0 libstemmer0d libsuitesparseconfig5 libtalloc2
  libteamdctl0 libtevent0 libumfpack5 libuno-cppu3 libuno-cppuhelpergcc3-3
  libuno-purpenvhelpergcc3-3 libuno-sal3 libuno-salhelpergcc3-3
  libunoloader-java libvisio-0.1-1 libwbclient0 libwpd-0.10-10 libwpg-0.3-3
  libwps-0.4-4 libxapian30 libxkbregistry0 libxmlsec1 libxmlsec1-nss libyajl2
  libyaml-0-2 libzmf-0.0-0 lightdm-gtk-greeter lp-solve
  mobile-broadband-provider-info mythes-en-us node-normalize.css openntpd orca
  p11-kit p11-kit-modules perl-tk pipewire pipewire-bin python3-brlapi
  python3-cairo python3-cups python3-cupshelpers python3-dbus
  python3-feedparser python3-gi-cairo python3-ldb python3-louis
  python3-musicbrainzngs python3-mutagen python3-pyatspi python3-pyinotify
  python3-smbc python3-speechd python3-talloc python3-uno python3-xdg
  quodlibet samba-libs sane-utils sound-icons speech-dispatcher
  speech-dispatcher-audio-plugins speech-dispatcher-espeak-ng
  sphinx-rtd-theme-common system-config-printer system-config-printer-common
  system-config-printer-udev uno-libs-private update-inetd ure usb-modeswitch
  usb-modeswitch-data usb.ids wpasupplicant xbrlapi xdg-desktop-portal xkbset
  xsane xsane-common
Use 'apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@localhost:/home/guest#

A reboot produces the devuan grub screen but boots to a prompt, not a xfce login.
Lightdm was removed early on and not reinstalled, yet. 

apt install lightdm

and it did boot to an X login screen, and it only needed one try to log in.

All logout buttons were working and not greyed out.

Note:  After installing XFCE, I had to enter the login information two times on the login screen.  I am sure I entered the correct login credentials.  After migrating, this problem went away.

CAVEAT - These are NOTES. They are NOT instructions. With a few more data points (supplied by you) we can hammer out some real instructions. (Hint: the yellow-highlighted commands might end up being the instructions.)

FIRST ATTEMPT

Failed. I tried to use nixer's method for buster to beowulf migration. Briefly, that involves doing the full migration to devuan with systemd still installed and running, and then rebooting into devuan with sysvinit at the end. See https://dev1galaxy.org/viewtopic.php?id=3044

This failed because it wanted to remove systemd while it was running. I also had a problem with apt wanting to remove the running kernel (5.10.0-7) because there's a newer one. I didn't bother to upgrade the debian system before the migration, but still, this is the first time I've ever seen an upgrade try to replace the running kernel. In the past, any dist-upgrades I did were happy to keep using the older kernel, even after the reboot.

SECOND ATTEMPT

Switched back to debian sources and apt-update failed, saying that bullseye-security doesn't have an InRelease file. I didn't get that error earlier, so it was probably a network glitch. I got around it by only enabling the one main repo line for bullseye.

Ran apt -f install as advised by apt.
apt install sysvinit-core
apt install linux-image-amd64 (which got removed earlier)
rebooted to sysvinit and linux-image-5.10.0-8 (still in debian)

Re-edited sources.list to chimaera
apt update (had to run dhclient to get network back)
apt dist-upgrade  (no errors!)
reboot (still had a large autoremove list, including Atril)

-----------------------------------------------------
This section should only be needed after installing from debian-live,
but you may still need to reinstall task-xfce-desktop

Got to console login on reboot. Lightdm was removed but slim was not installed.
task-desktop and task-<language>-desktop are installed, but not task-xfce-desktop.
To remove all the language packs, apt remove task-* (This is only needed after installing from debian-live.)
then
apt install task-desktop task-xfce-desktop  (this brinds in slim, synaptic, network-manager)
apt autoremove
reboot
OK! No network connection and boot menu still says Debian.
-----------------------------------------------------

I messed with network-manager and /etc/network/interfaces.d/setup in every way I could think of, and I still can't get a network connection.

Rebooted a live-iso with the virtual disk attached.
In chroot:
installed lsb-release and ran update-grub. That changed the boot menu to say Devuan.
also installed dnsutils thinking that might help.

After reboot, I still couldn't ping by name or number (even as root) but I tried a web browser, and I do have network.