I recently tried around 12 hrs ago. Making a post with “English” did not give any error but got stuck at the Loading icon of the create button. The same post got submitted successfully when choosing Undetermined. This was with Firefox The same happened when I tried to choose “English” for this comment.

Doesn’t work for me either. Tried some other random language and it didn’t work either, so I’m assuming only “Undetermined” works.