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.
I mean jmp let's you use only the integrated player or cast to mpv shim.
I can play the files with mpv, vlc or Kodi without issues but I would like to use something like plex/jellyfin for all the other capabilities they offer like playback position syncing and so on.
It's kind of mild here but very noticeable in really dark parts of the scene. Makes a lot of stuff pretty bad.