It is probably a very specific issue, since I can’t find anyone else that has it, at least not doing the usual google-fu.
When using the Stremio web client, firefox refuses to play anything I throw at it, whereas everything plays fine in the chromium browsers I’ve tried.
No amount of turning extensions off or clearing cache or cookies or refreshing has fixed it so far.
Link to relevant article: https://magazine.columbia.edu/article/pacifists-guide-satanism