Just tested and with Findroid on my phone, no subtitle options appeared at all, though it had 4 languages embedded. On my roku they showed up but as soon as I picked it it loaded until it said Error During Playback

Sounds like it’s mostly with embedded subs inside the media files already. Thats where all my subs are so I’m going to test soon but haven’t played anything on jellyfin needing subs in a while

I’ve been using plex for several years and setup jellyfin a few months ago to tinker with it. Playing videos works fine for me locally but I have some family out of state who have access and jellyfin doesn’t have a solution for that outside of me publicly sharing the URL and managing the passwords. Also a pain point for me is having multiple files of different quality for the same movie/episode, it always shows as two episodes that it will play back to back and seems to require a lot of manual work per show/movie to get it tracked as 1 piece of media with 2 files to choose from. Would love to ditch Plex eventually but for me and my family it just works without issue and they can manage their own remote login.