According to Google, this is the solution

AppCompatDelegate.setApplicationLocales(LocaleListCompat.forLanguageTags(locale));

and use not the regional tag r. As in my example kq-GN

NB! This code is working from Android Tiramisu and up

My problem is that even this code is not working. The app will not change to any language with this code. If I try to run this

AppCompatDelegate.getApplicationLocales().toString());

I get this output []

I even get this result before I do the switch of language, so it seems that there is something wrong here.