How do you know if a picture was taken on fall? I'm joking, guess MM is for month. Anyway, YYYY-MM-DD is ISO-8601 compliant and better.
If I understand correctly, you want to add the filename as a watermark in your pictures? Do you know python? Pretty sure there must be some python library that can help you with that. Try asking some AI LLM it should not be that complicated.

Silksong is also native on Linux