Recommended OS for Jellyfin client

[Host-in-the-Shell]

There's really no good alternative unless you don't particularly care about HDR passthrough, as HDR isn't much of a thing under Linux yet. You'd have to run KDE which has a subpar implementation or use gamescope which is geared towards gaming more than anything.

Not to mention that with Libelec/Kodi you're already compromising by not having HDR to SDR conversion (through something like tonemapping for instance) in the first place. Also, no Dolby Vision support, since it only works for Kodi under Android and with a device that is licensed for it; otherwise it can't decode it.