Chris wrote:
Good news, nothing's broken on your end. That SparkBox setting only turns on the connection to your Ugreen's graphics chip -- Jellyfin itself still needs to be told to use it separately. In Jellyfin, go to Dashboard Playback, set Hardware acceleration to VAAPI, and enter the same /dev/dri/renderD128 path you already set in SparkBox, then save. Right now playback is likely falling back to software encoding, which keeps up fine at 20mbps but chokes at 40mbps -- once Jellyfin's own toggle is flipped it should stop stuttering.