SUMMARY If I configure my timezone/location to a locale which does not have the ".UTF-8" portion during installation, for example for India (Asia/Kolkata timezone) or Nigeria (Africa/Lagos timezone), the installer (Calamares) says it will set it to "English (India)" or "English (Nigeria)". After booting into the installed system and going to the region+language settings it shows only "English" instead of the expected "English (India)" or "English (Nigeria)" although the remaining parts like Currency, Phone numbers etc appear correct. Upon clicking the CHANGE button there is a toast/popup at the top with the error message "The language en_IN is unsupported" for India or "The language en_NG is unsupported" for Nigeria. STEPS TO REPRODUCE 1. Install KDE (with Calamares) with a timezone/locale that does not have the ".UTF-8" portion such as India en_IN (Asia/Kolkata) or Nigeria en_NG (Africa/Lagos). 2. Boot into the installed system and go to the region+languages settings page. 3. Observe the language only shows "English" and not "English (India)" or "English (Nigeria)". 4. Click the CHANGE button. OBSERVED RESULT Error message/toast/popup: The language "en_IN" is unsupported. Unable to select a language like "English (India)" which does not have the ".UTF-8" portion in /etc/locale.gen list. EXPECTED RESULT No error message should appear and languages like "English (India)" or "English (Nigeria)" (which appear in /etc/locale.gen as en_IN or en_NG without the ".UTF-8" portion) should be available to select. SOFTWARE/OS VERSIONS Linux/KDE Plasma: 6.4.x KDE Plasma Version: 6.4.x
Likely the following? https://invent.kde.org/plasma/plasma-workspace/-/blob/master/kcms/region_language/languagelistmodel.cpp#L32 and https://invent.kde.org/plasma/plasma-workspace/-/blob/master/kcms/region_language/languagelistmodel.cpp#L107
Plasma doesn't have translations for English (India) and English (Nigeria), thus unsupported.