How to set a language's default locale

[Alexander Becker]

Good evening, Charlotte!

   > Currently, when trying to load the language "Gaeilge" (ga), KDE is 
trying to use the "ga_IE.UTF-8 at euro" locale by default in 
`~/.config/plasma-localerc`, which doesn't exist in glibc.

1. Are you sure "Gaeilge" is correct, 
https://l10n.kde.org/stats/gui/stable-kf6/team/ga/ says "Irish Gaelic (ga)".

2. Why do you think your locale is not supported by glibc?
    git clone https://sourceware.org/git/glibc.git
    cd glibc
    git log | grep ga_IE
    => here I could see both ga_IE and ga_IE at euro locales

   > which doesn't exist in glibc. Due to this, a lot of programs don't 
work or produce errors when trying to run a system in the language.

3. I have tried locally in konsole:

   LANGUAGE=ga gwenview
   LANGUAGE=ga_IE gwenview
   LANGUAGE=ga_IE at euro gwenview

   Or for flatpak versions of apps:

   flatpak config --set extra-languages ga
   flatpak config --list
   flatpak update
   LANGUAGE=ga flatpak run org.kde.kate
   LANGUAGE=ga_IE flatpak run org.kde.kate
   LANGUAGE=ga_IE at euro flatpak run org.kde.kate

   → In all variants I could see strings in your language and no errors. 
Which errors do you have (locale related)?

By the way: If you want to test newest translation which is not yet part 
of an application (e. g. Dolphin) you could do following:

   msgfmt dolphin.po -o dolphin.mo
   mkdir -p ~/.local/share/locale/ga/LC_MESSAGES
   cp dolphin.mo ~/.local/share/locale/ga/LC_MESSAGES
   # start Dolphin and check new translated strings

I hope it will help you and your team.

Best regards
Alexander