You confuse me. What is the problem, really?
The installer doesn't build any md assemblies by itself. And the raid1 setup seems fine.

However the lack of a bootloader partition for grub on the boot disk is a problem. You should have /dev/sda1 or /dev/sdb1 partitions assigned as BOOT_bios partitions for grub to use (choosing which is the boot disk). So you can't use them in a raid and you can't install a filesystem on them.

I've now set up a VM with 2 disks /dev/sda and /dev/sdb, with some 8 partitions each, to form 7 raid1 assemblies, while /dev/sda1 and /dev/sdb1 are set up as "BIOS boot" partitions for grub. Though only /dev/sd1 is in use for booting.

The key step for making it work is to not install grub via the installer but by hand from the C-A-F2 console, and then bind-mount /run from the installer onto
/target/run before the chroot into /target and the grub installation.

If you missed out on that, you can recover by starting the installer in menu choice 1, and progress that to the hostname dialog; then go to C-A -F2 console for recovery actions, for example:

# mdadm -C -n2 -x0 -lraid1 -v /dev/md0 /dev/sda2 /dev/sdb2
# mount -t ext4 /dev/md0 /mnt
# mount --bind /run /mnt/run
# chroot /mnt /bin/bash -i

and continue in the chroot

# mount -t proc proc /proc
# mount -t devtmpfs dev /dev
# mount -t devpts devpts /dev/pts
# mount -t sysfs sys /sys
# mdadm --assemble --scan
# mount -a
# apt-get install --reinstall grub
# update-grub
# grub-install /dev/sda
# update-initramfs -u
# exit

and then

reboot

The above is on the assumption that md0 has sda2 and sdb2, and contains the root filesystem. Further /etc/mdadm/mdadm.conf must be duly prepared; but the key is still to have md0 assembled in the console and then that /run is bind-mounted into the chroot before you go into that for the further rescue actions.

HTH

Did you actually run that sed command?
I copied and pasted from your post #14 and got a file of 1603 bytes.
That is the size of the file in your post #22
I then ran that sed command and got a file of 1598 bytes.
The differences are in removal of space characters on the blank lines.

Perhaps you have different explanation why your file is 1603 bytes?

Can you post output of ls -l /etc/apt/sources.list*

Ha! You're right. I interpreted that condition wishfully rather than correctly.

So obviously, would I want to use nfs, I need to arrange for that by myself since I wouldn't find joy in associating nfs mounting with networking events.

And if I choose to install a system with a Devuan installer iso and select a desktop flavour that installs NetworkManager, I will need some additional post-install hands-on to purge that together with apparmor, avahi-daemon and whatnot that the desktop flavour developers have included at the outside of my ideal setup.

Traditionally, NFS mounts are set up as declared in fstab via the init script mountnfs.sh, and it's not as a side effect of networking. That kind of NFS mount is supported with sysvinit, and it works as fine with excalibur as it has done with prior repository codenames.

Clearly one may insist on some different NFS mount behaviour.. In such a case one will need to set up the system to support that.

Yes it does... I'll try it out to see if I get the same. Will take a little while though.
Did you install with or without network?

@Andre4freedom: please show the error log, from the boot with fstab set up as in your daedalus. (It's awfully hard to just guess)

Probably logged to /var/log/dmesg and/or /var/log/syslog.

It's not that hard:

* start with an opening square bracket, the word code, a closing square bracket

* end with an opening square bracket, a slash, the word code, a closing square bracket

Or maybe you want it to be a bit peculiar?

check out man cryptsetup

I'm using forums.debian.net... it seems available but different. (I haven't noticed before that the header includes "Debian Fish and Animal Emporium", whatever that means.)

EDIT: apparently an April 1 joke that was so hilarious for the admins that it has remained. "Fun" is something subjective, obviously.

I'm more puzzled by your statement "don't want to open a debate" than anything. But I agree that using elogind or not is not really something worth debating.