To your last question, what do you mean by arbitrary? If the video is not educational at all, then the generated course will likely not be good. If the video is pure entertainment then probably not a good use case.
Yea YouTube is only one format we support. Users can also upload pdfs, mp4, docx, pptx, etc. And we already do support video hosting ourselves. It wouldn't be great if YouTube decided to part ways with us, but we'd be just fine.
Poker is interesting. I think these videos do work in our current course generation process. However, I do think some subjects like poker need custom tooling around the course to really make the learning experience great. For example, access to solvers or actually playing a hand on a table is a part of the course experience as well. Chess is another one that falls in this special bucket imo. Some of this tooling is on the roadmap!
Users can upload slides (ie. docx or pptx) and create a course from them - give it a try! For videos, we don't currently process any frames from the video just the transcript, but this is on the roadmap.