AppleTV client at some point?
Is there currently any? This is the only reason I’d consider moving from plex.
There’s the official Jellyfin app for Apple TV. It works very well with only minor UI bugs when browsing libraries. Nothing that detracts from or reduces the quality of the service.
Surround sound didn’t work for me with the Jellyfin player and with the native player language selection didn‘t work. If you don’t have to transcode and spare a few quid, Infuse is great. Sadly can’t recommend it to my friends accessing my server from outside my home network because of said lack of transcoding.