...
LANG=nds_DE.UTF-8
LANGUAGE=de
...
I realized recently that in some dropdown lists if you want to select german by typing 'de', the cursor jumps to
nde_DE. But be aware that
nds is Niedersachsen, do you really want Platt

? Probably that's not fully translated yet. Reconfigure again and assure that you really select
de_DE.UTF-8, then try again.