Additional languages at regional settings lead to CLI errors are printed at unexpected - not default - languages

[Martin Bruzina]

Let's try with fresh install: Kubuntu 20.04.1 with default installer options + all packages updated, upgraded:

0. Test current CLI error messages with an intentionally faulty command for later comparison:
   apt install -y nonsense
   Result:
   E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
   E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
1. Go to System settings -> Regional settings -> Language
2. Add 3 languages: čeština, slovenčina, русский in order as listed, keep American English (default) as the first language
3. Apply
4. Logout
5. Login
6. Test again current CLI error messages with an intentionally faulty command:
   apt install -y nonsense
   Result:
   E: Nešlo otevřít zámkový soubor /var/lib/dpkg/lock-frontend - open (13: Permission denied)
   E: Невозможно получить блокировку внешнего интерфейса dpkg (/var/lib/dpkg/lock-frontend); у вас есть права суперпользователя?
   Expected:
   E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
   E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?

As a user, I expect that the topmost and default KDE language would be used for CLI errors as the primary one.

[gl.bars (gl-bars)]

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[Martin Bruzina (bruzina)]

The issue is present on Kubuntu 22.04.2 as well.