Missing locales in KDE Plasma

Help
1

Whenever I go to System Settings > Region and Language, then try to change any one of the options, I find that there is no other locale option in the menus except for my current locale, when there should be a whole list of languages present.

Here are some screenshots to demonstrate. Note that the Settings app looks a bit different since I’m using Breeze with a custom color scheme.

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The Measurement section is missing an entire list of locales that are supposed to be there. The same is true for all sections between Language and ‘Data and Storage Sizes’, excluding those sections themselves.

I have the following set in my NixOS configuration regarding locales:

{
  i18n = {
    defaultLocale = "en_GB.UTF-8";
    extraLocales = "all";
  };
}

Here’s some info about my system:

  • NixOS version: 26.05
  • KDE Plasma version: 6.6.6