“If the picture is black but the audio is still playing, you should go back and select a stream with a different resolution.“
This is actually a fire stick specific issue relating to HDR 10 and Dolby Vision. TLDR is use the Kodi patch here: https://github.com/jellyfin/jellyfin-androidtv/issues/2630#issuecomment-1504463357 and set the external player option in Stremio
I would get a premium trial and share any playlists on the account you don’t want to lose for the development of your tool. Worked for me when exporting my 4000~ song playlist.