The Apple TV solutions for Jellyfin are inadequate last I checked. Basically you are stuck with Plex and Infuse. I already have lifetime Plex Pass so no reason to care... for now.
I ditched plex because of missing Dolby audio support and all the use hostile channels and “features” years ago, and will never look back.
Paying more money to use a different product, and then expecting all of my users to do the same, is a big hill to climb.
So the Plex inertia remains.
One caveat is that older AppleTVs can’t do native decoding of some mkvs. But that’s largely an AppleTV limitation. Though I could imagine the client being smart enough to list its abilities and the server only serving content supported by the client.