SUMMARY So the problem is Plasma uses a language that has been deleted the previous session. This can be fixed be re-logging in a second time, but although I can reproduce this problem consistently, it is probably not intended. STEPS TO REPRODUCE 1. Add a second language (If only one is installed) (If you installed a language in step 1): 1.2 Restart and log in 2. Remove The second language 3. Log out 4. Log in OBSERVED RESULT Plasma uses the language that was deleted in the previous session EXPECTED RESULT Plasma uses the only installed language. SOFTWARE/OS VERSIONS Linux: 5.15.12 KDE Plasma Version: 5.23.4 KDE Frameworks Version: 5.89.0 Qt Version: 5.15.2