In my case, I was not able to make jellyfin work: transcoding issues, lagging, client disconnection or unresponsive... Plex worked flawlessly out of the box with the same hardware and the same library.
From time to time I try Jellyfin again, but things never change ..
Thank you, but it won't be necessary. I think my issues are hardware -related, or simply my NAS is under too much load from other applications 😅 Other than that I should try with the Chromecast as you suggested, maybe the problem was the shitty client application...
If I don't succeed I'm still good with Plex, and I have a raspberry hanging around for an emergency Kodi.