Hi! As far as I know a warning about Undetermined languages should show up in a box in the Settings page, but instead the text "undetermined_language_warning" shows up. I think that's a bug.
Before lemmy.ml was down I remember the message correctly showing on my account on that instance.
on the lemmy.world instance, the warning reads
as in, content is probably
Undetermined
by default, so make sure that it's selected (along with whatever other languages you prefer). You can select multiple languages by holding down the Ctrl/Command? buttons on your keyboard while you click the other languages.