We tested it on CommonVoice German, which is what Mozilla used for DeepSpeech German, too. The idea behind that dataset is that arbitrary people on the internet submit their recordings (hence the "common" in the name) and then if enough other people upvote it as "understandable", it gets included in the dataset.

As such, the AI works well with a variety of accents.

I suspect that "works well" means that the model will output words in "official german" and kind of corrects pronounciation errors? I am asking because I had the use case to automatically give feedback to non native german speakers.

There's a command-line parameter "--use_language_model=0" to disable the spellchecker.