2.54.3+21.10.1ubuntu0.1 broke Plasma Desktop when Fish is the default shell

Interesting information from a Fish Shell developer:
https://github.com/fish-shell/fish-shell/issues/8741#issuecomment-1047801157

Other workarounds:
* Using LightDM instead of SDDM: https://askubuntu.com/q/1394269/1573362
* Changing your local Fish configuration: https://github.com/fish-shell/fish-shell/issues/8741#issuecomment-1047820309

Status changed to 'Confirmed' because the bug affects multiple users.

Other trivial workaround: keep snapd to 2.44.3 (at least on 20.04), possibly forever. There's a serious QA problem here, in a week I got three updates, each of which progressively broke stuff worse than the previous one:

- first warnings every time I opened a shell
- then broken XDG env, which made applications crash in the strangest ways but only when started from the shell
- then even more broken XDG env that literally _broke the user session after login_.

I don't think a bug can get worse than this, as it makes the machine (progressively more) impossible to use _for tasks unrelated to those for which you need this package_, and, with the exception of the first problem, without any hint about the fact that it's snapd fault — in the last case I only suspected that (and downgraded) because I was bit by the first issue, I had to debug the second one, and it dawned on me that they could have fucked up the fix for a third time after managing to open a shell inside the broken session through strange expedients and checking the environment.

I get that the Linux desktop environment initialization is a shitshow, but after breaking this for the first time the response should have been immediate rollback and _thorough_ testing instead rushing fixes, at least on the LTS channel.

This bug was fixed in the package snapd - 2.54.3+21.10.1ubuntu0.2

---------------
snapd (2.54.3+21.10.1ubuntu0.2) impish-security; urgency=medium

  * SECURITY REGRESSION: Fix fish shell compatibility
    - data/env/snapd.fish.in: more workarounds for even older fish shells,
      provide reasonable defaults.
    - LP: #1961791

 -- Paulo Flabiano Smorigo <email address hidden> Wed, 23 Feb 2022 14:48:54 +0000

This bug was fixed in the package snapd - 2.54.3+20.04.1ubuntu0.2

---------------
snapd (2.54.3+20.04.1ubuntu0.2) focal-security; urgency=medium

  * SECURITY REGRESSION: Fix fish shell compatibility
    - data/env/snapd.fish.in: more workarounds for even older fish shells,
      provide reasonable defaults.
    - LP: #1961791

 -- Paulo Flabiano Smorigo <email address hidden> Wed, 23 Feb 2022 18:25:31 +0000

This bug was fixed in the package snapd - 2.54.3+18.04.2ubuntu0.2

---------------
snapd (2.54.3+18.04.2ubuntu0.2) bionic-security; urgency=medium

  * SECURITY REGRESSION: Fix fish shell compatibility
    - data/env/snapd.fish.in: more workarounds for even older fish shells,
      provide reasonable defaults.
    - LP: #1961791

 -- Paulo Flabiano Smorigo <email address hidden> Wed, 23 Feb 2022 18:29:05 +0000