Cannot update/install openssl (or any) package; "Unmet dependencies" "E: Sub-process /usr/bin/dpkg returned an error code (1)"

Question

Thank you for reading this.

I am having difficulties updating installing packages on a raspberry pi.

Disclaimer: I am a massive linux noob, please be gentle.

Note: I am doing this over SSH, in case this has something to do with it.
My raspberry pi used to run on jessie, but I updated it to bullseye, which (may have) lead to the problem.

My problem

Since pip wasn't installing anything, (SSL errors) I looked it up and found out I might have to upgrade openssl, but it wouldn't work.

I tried this with many other packages and got the same issues.

Whenever I wanted to install anything after the upgrade, I would get "Unmet dependencies"
I looked it up and tried apt install -f and the same with apt upgrade openssl -f

But I would always get

E: Sub-process /usr/bin/dpkg returned an error code (1)

Here is an example, when installing vim:

pi@raspberrypi:~ $ sudo apt-get install vim
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies:
dpkg-dev : Depends: libdpkg-perl (= 1.20.9) but 1.18.25 is to be installed
            Recommends: build-essential but it is not going to be installed
  vim : Depends: vim-common (= 2:8.2.2434-3) but 2:7.4.488-7+deb8u4 is to be installed
        Depends: vim-runtime (= 2:8.2.2434-3) but it is not going to be installed
        Depends: libgpm2 (>= 1.20.7) but 1.20.4-6.1 is to be installed
        Depends: libtinfo6 (>= 6) but it is not going to be installed
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).

pi@raspberrypi:~ $ sudo apt --fix-broken install

... Lots of lines of output, log can be found here

Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)

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I found online I could probably update dpkg, but I'm not completely sure on how to do that. dpkg at this point is completely unusable, even downloading the latest dpkg and loading it with dpkg -i new_dpkg.deb won't do anything.

So did I screw up my system, or is it just PEBKAC?

If it's the former, how would I go about fixing it?

Many thanks in advance and sorry for the noob question

---

Other info:

os-release, sources.txt, dpkg configure a: here

Edit: I think it may have to do with the sources.txt, make sure to click the link above

Answer 1

Your question and its links show a mix of multiple releases of Debian/Raspbian either in current state or configured repository sources with clashing package versions:

• 8 +11 ("Depends: vim-common (= 2:8.2.2434-3) but 2:7.4.488-7+deb8u4 is to be installed")
• 9 + 11 ("Depends: libdpkg-perl (= 1.20.9) but 1.18.25 is to be installed")
• 11 (link shows PRETTY_NAME="Debian GNU/Linux 11 (bullseye) ).

and apparently no trace of version 10.

Distribution upgrades should be done one step at a time: 8 -> 9 -> 10 -> 11, and not be attempted before the previous upgrade is completed without remaining issues. Here it appears 8 -> 9 wasn't complete but was nevertheless followed by an attempt to upgrade to bullseye (soon to be released as version 11 but not officially released) and it appears also without a step at version 10.

Repairing multiple layers of problems caused by this appears not worth the trouble. You should consider backing up important data and user accounts and reinstalling directly (eg: with Raspberry Pi OS 10), and then putting back former data (which might require adapting to newer versions) and user accounts.