Did they abandon the Flatpak package? The Jellyfin Player Flatpak is up-to-date, but the Server package on Flathub is at 10.8.13 and no longer listed on the Jellyfin website
EDIT: Looking at an archive from earlier this year, the Flatpak was tagged as "Community", not "Official". So I guess I shouldn't be too surprised that the random packagers did not keep up with releases.
I had no issue with it when I set it up on my Steam Deck. Setting up docker/podman through distrobox or something just seems like so much extra hassle compared to a Flatpak.
Because even without Flatpak, there's plenty of other package for different distros that are easy or easier than flatpak. You don't have to go all the way to a docker.
It's probably best to do it eventually but it doesn't have to be today.
Yes, installing/running Jellyfin Server on Steam Deck. What would be the best way to install on an immutable OS like SteamOS where Flatpak is typically the go-to?
If you really want it as a flatpak you could attempt to build your own with up to date versions. However that would likely take longer than using an official package.