I've been a long time jellyfin user but I haven't been able to ditch plex completely because of this problem. On my linux system with nvidia, with hardware decoding enabled/off/copy or with any of the codecs, I get this weird color bands in video when I use JMP. It doesn't happen with the plex app or when directly using mpv with the jellyfin-mpv ship. I have identical mpv config files for mpv for JMP and my system, with vanilla mpv having no issues.
I am at my wits end regarding what might be causing this and I end up using the plex app even though I hate the interface.
JMP:
Plex App:
MPV:
And using the browser-based client isn't an option? I heard PWAs are pretty well supported on linux...
PWAs are not an issue but hardware acceleration is pretty broken on Wayland and Nvidia combo.