I had a similar issue on a different panel where the back light and on/off would function, but no menu would show. I found that I’d inserted the LVDS ribbon cable the wrong way up on the controller connector.

Why not a PiZero running browser as a client? I had 4 PiZ in a K8s cluster and they did well. I still have a few running streaming cameras for a 3D print farm. Put MM server in a docker container on the RPi4.