There’s no official Jellyfin app for TvOS. There’s a couple of apps that a log into JellyFin, but they all seem rough around the edges UX wise. Most of them do not have ability to search, nor filter watched movies/shows. You shouldn’t have any problem with setting up JellyFin, you just point it to your video library and it does its thing just like Plex. If you have multiple users, plan on having to do some reeducation on why things look and work slightly differently.

Overall JellyFin is a slight downgrade in the UX compared to Plex, especially on the Apple TV, but should function the same in playing videos.

What all did you do to get it working? I’m stuck with this issue.

I dislike that the sans serf font makes the capital i look like a lowercase L