Honestly it just works and works well. I had all sorts of issues with Plex with subtitles not working and weird transcoding issues where red blocks would randomly appear. Also I found Plex kinda ugly tbh. I tried Jellyfin and it seemed a bit ‘hacky’ but this was a few years ago so maybe it’s improved but I currently have no reason to try it again. If you’re using Plex/Jellyfin/Emby you are most likely pirating media so worrying about GPL violations is probably not top of the list.

Try Emby. It’s a more polished Jellyfin although it’s not FOSS I find it much better than Plex