I tried this with zeroPi and jellyfin, bit the Pi seemed constantly overwhelmed with displaying videos, so I got about a frame every 2 seconds (might have been a pi3b). Have you got any clue what the issue might be? It depended a lot on the particular file I wanted to play as well though, but I wasn’t able to find a pattern. Of two matroska/mp4 files one worked well, the other stuttered as hell.