Not sure if this will make any difference, but please try to disable both cellular and wifi then re-enable the wifi only and reconnect to the network?
I tried this and also a combination of switching the WIFI, cellular, airplane mode, Bluetooth. None of which is making any difference.
I did find that SpaceDesk app is not in the app list of “APPs using wifi and cellular” though, not sure if this has anything to do with the problem.
I am now inclined to believe maybe this problem has something to do with the cellular function, and I will test it whenever I can get hold of another wifi-only iPad. I will keep you posted.