Since the last update, only "American English" is listed "in the "Languages" tab of systemsettings's regional settings, though the German (de) locale is installed. Also, the UI elements to add additional languages have disappeared. While German continues to be present in most of the desktop UI, the keyboard was reset from the (German) QWERTZ layout to the (int'l) QWERTY layout. Reproducible: Always Workarounds: "setxkbmap de" works to restore German keyboard layout. In the input devices->keyboard, I can also manually add and prioritize the "de" layout. Still, the underlying problem remains.
The Language module was rewritten in 5.13. Please reopen if this continues to be a problem.