I did not install the piece of trash but did download and extract the package and its data payload. It puts the browser in the opt directory and nowhere is there to be found a gpg key. They install a cron job file which when trying to look at has nothing in it so it is a bit of a mystery what it does. I tried their junk once many years ago and gave up once I discovered they were more interested in controlling their "smart" lights from the browser than actually fixing the bugs I reported. My reward for that effort was constant spam from the scumbags on the email that reported the bugs such that I had to create a special filter for anything coming from them going straight to /dev/null. That is the type of people you deal with when using it.

You are welcome, probably should have done that myself while replying, I never tested it on my machine which would have shown my mistake in thinking a comment (the # in the line for it being ignored) would work there.

Of course it is the same as the security, you would add both of them back in once they are created some time next year before the next release and the proposed-updates as well. You have until 2030 or so as well but you should consider switching too the new format devuan.sources too. My current file that has all of these things enabled.

root@9600k:~# cat /etc/apt/sources.list.d/devuan.sources 
## Devuan 6 excalibur
## The new style method of using repositories to install software.
## This /etc/apt/sources.list.d/devuan.sources is new style and location file
## The /etc/apt/old.style.sources.list contains the same as this.
## https://linuxconfig.org/ubuntus-repository-configuration-ubuntu-sources-have-moved-to-etc-apt-sources-list-d-ubuntu-sources

## Normal excalibur sources
Types: deb
URIs: http://gnlug.org/pub/devuan/merged 
Suites: excalibur excalibur-backports excalibur-proposed-updates  excalibur-updates
Components: main non-free contrib non-free-firmware
Enabled: yes
Signed-By: /usr/share/keyrings/devuan-archive-keyring.gpg
Architectures: amd64

## excalibur security sources
Types: deb
URIs: http://gnlug.org/pub/devuan/merged
Suites: excalibur-security
Components: main non-free contrib non-free-firmware
Enabled: yes
Signed-By: /usr/share/keyrings/devuan-archive-keyring.gpg
Architectures: amd64

It is rather easy to switch sudo mv /etc/apt/sources.list /etc/apt/old.style.sources.list then sudo nano /etc/apt/sources.list.d/devuan.sources with this as its contents.

## Devuan 7 freia
## The new style method of using repositories to install software.
## This /etc/apt/sources.list.d/devuan.sources is new style and location file
## The /etc/apt/old.style.sources.list contains the same as this.
## https://linuxconfig.org/ubuntus-repository-configuration-ubuntu-sources-have-moved-to-etc-apt-sources-list-d-ubuntu-sources

## Normal freia sources
Types: deb
URIs: http://gnlug.org/pub/devuan/merged 
Suites: freia #freia-backports freia-proposed-updates  freia-updates
Components: main non-free contrib non-free-firmware
Enabled: yes
Signed-By: /usr/share/keyrings/devuan-archive-keyring.gpg
Architectures: amd64

## freia security sources
Types: deb
URIs: http://gnlug.org/pub/devuan/merged
Suites: freia-security
Components: main non-free contrib non-free-firmware
Enabled: no
Signed-By: /usr/share/keyrings/devuan-archive-keyring.gpg
Architectures: amd64

Then sudo apt update to refresh the mirrors package list. Once the freia is released remove the # in the Suites line to have them used and change the no to yes in the security part to enable it and you will be good to use all of them. You can change the URIs line to be  http://deb.devuan.org/merged to continue using the round robin mirror selection you currently use if you wish. Also if you ever need package sources for your install the Types line can have deb deb-src there to enable the fetching of source packages.

Edit: And since you ask about upgrading then the procedure for that is before changing to the new freia sources do an sudo apt update and sudo apt upgrade to have the latest for everything installed once everything is done then sudo apt update and sudo apt full-upgrade when you have changed to the freia sources file.

What makes you think that? Have you looked into the file and confirmed this? Also posting the output of the update-grub command would be helpful to be able to see what it does when it runs, mine for instance.

root@9600k:~# update-grub
Generating grub configuration file ...
Found theme: /usr/share/desktop-base/grub-themes/desktop-grub-theme/theme.txt
Found linux image: /boot/vmlinuz-6.12.57+deb13-amd64
Found initrd image: /boot/initrd.img-6.12.57+deb13-amd64
Found linux image: /boot/vmlinuz-6.12.48+deb13-amd64
Found initrd image: /boot/initrd.img-6.12.48+deb13-amd64
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...
done

Edit: and now I think of it.

What is the matter with sudo apt autoremove which would have done it by removing the third oldest entry the -35 version leaving the last two version that were installed by apt, the method of doing it in/on a Debian based system. Adding the --purge option to that command is always a good idea to get rid of the leftover cruft it leaves behind without it used.

Remove the damn thing then it has no chance of starting again.

sudo apt remove --purge mate-polkit

Used in a Terminal to do the actual removal.

sudo rm /etc/apt/keyrings/keyring-2022-archive.asc
sudo rm /etc/apt/keyrings/keyring-2016-archive.asc

Used in a Terminal if in old location if in the new then /usr/share/keyrings/ could be the location to remove them from.

Then sudo apt install libxapian30 and since the system is borked from trying to install the -dev package sudo dpkg -r --purge synaptic-build-deps you may want to do that first. This is why I dislike those GUI programs they do nothing to show you how the system works and leaves you unable to solve even the most basic of problems due to this lack of eperience.

This is from the control file I extracted from the downloaded .deb file from that location.

Package: synaptic
Version: 0.91.7+nmu1
Architecture: amd64
Maintainer: Michael Vogt <mvo@debian.org>
Installed-Size: 7805
Depends: libapt-pkg7.0 (>= 1.9.0), libc6 (>= 2.38), libgcc-s1 (>= 3.0), libgdk-pixbuf-2.0-0 (>= 2.22.0), libglib2.0-0t64 (>= 2.14.0), libgtk-3-0t64 (>= 3.21.5), libpango-1.0-0 (>= 1.14.0), libstdc++6 (>= 14), libvte-2.91-0 (>= 0.49.92), libxapian30 (>= 1.4.28~), hicolor-icon-theme, polkitd | policykit-1, pkexec | policykit-1
Recommends: libgtk3-perl, xdg-utils
Suggests: dwww, deborphan, apt-xapian-index, tasksel, software-properties-gtk

Very few packages needed and looking at the same package it appears before it gets cut off by my Terminal width it is going to list exactly the same packages.

zeus@9600k:~$ apt show synaptic
Package: synaptic
Version: 0.91.7
Priority: optional
Section: admin
Maintainer: Michael Vogt <mvo@debian.org>
Installed-Size: 7,975 kB
Depends: libapt-pkg7.0 (>= 1.9.0), libc6 (>= 2.38), libgcc-s1 (>= 3.0), libgdk-p>
Recommends: libgtk3-perl, xdg-utils
Suggests: dwww, deborphan, apt-xapian-index, tasksel, software-properties-gtk

So all of them dependencies shown should already be installed on your machine, I am failing to see how it wants to install all those extra packages you say it does. The git failure in your previous posting is due to it not being installed. Show us the output of the sudo dpkg -i /path/to/downloaded/synaptic_0.91.7+nmu1_amd64.deb.

Yes if you have the build-essential and build-depends for synaptic installed that should probably do it. I doubt the package you got is built for Debian 13/Devuan 6 a simulated install here shows very few packages needed for a fresh install.

root@9600k:~# agis synaptic

Installing:                     
  synaptic

Installing dependencies:
  libcairo-gobject-perl  libextutils-depends-perl           libglib-perl
  libcairo-perl          libglib-object-introspection-perl  libgtk3-perl

Suggested packages:
  libfont-freetype-perl  dwww       apt-xapian-index
  libxml-libxml-perl     deborphan  software-properties-gtk

Summary:
  Upgrading: 0, Installing: 7, Removing: 0, Not Upgrading: 1
Inst libcairo-perl (1.109-5+b1 Devuan:6.0/stable [amd64])
Inst libextutils-depends-perl (0.8002-1 Devuan:6.0/stable [all])
Inst libglib-perl (3:1.329.3-3+b3 Devuan:6.0/stable [amd64])
Inst libcairo-gobject-perl (1.005-4+b4 Devuan:6.0/stable [amd64])
Inst libglib-object-introspection-perl (0.051-2+b1 Devuan:6.0/stable [amd64])
Inst libgtk3-perl (0.038-3 Devuan:6.0/stable [all])
Inst synaptic (0.91.7 Devuan:6.0/stable [amd64])
Conf libcairo-perl (1.109-5+b1 Devuan:6.0/stable [amd64])
Conf libextutils-depends-perl (0.8002-1 Devuan:6.0/stable [all])
Conf libglib-perl (3:1.329.3-3+b3 Devuan:6.0/stable [amd64])
Conf libcairo-gobject-perl (1.005-4+b4 Devuan:6.0/stable [amd64])
Conf libglib-object-introspection-perl (0.051-2+b1 Devuan:6.0/stable [amd64])
Conf libgtk3-perl (0.038-3 Devuan:6.0/stable [all])
Conf synaptic (0.91.7 Devuan:6.0/stable [amd64])
root@9600k:~# alias agis
alias agis='apt -s install'

Always possible if you know the packages required to be be installed to have them used again. Then you need to stop updating the system or have put them packages on hold to stop them from being updated until new packages arrive that fix the broken mess. Either way it requires someone who knows their way around the system and the pitfalls of using it with the skills to fix it once broken.

Should just be a simple sudo dpkg -i synaptic_downloaded.deb which will overwrite the version installed. With its higher version number as it has the +nmu1 added to the version number telling the system that it is newer higher versioned packaged than the plain 0.97.1 installed now.

I went with the Waterfox after going on twenty-eight years of use, since the fork from Netscape that later become Firefox, them idiots at Mozilla finally got me to give it up with this latest bunch of BS they pulled. It has been building for years now with all the trash changes they have made but that announcement was the straw that broke the camels back. The Waterfox works great everything just runs like it did except my fonts look much better for some reason, using the same ones too.

If they had listened they would have heard all the complaints when the first put that garbage into the browser and did bury it in about:config. All that is now is damage control now they have been seriously called out on their scummy behaviour towards us.