Passthrough Problems after Unity upgrade

Hi,

I just switched to Unity 2021.3.25f1 and Oculus XR Plugin 3.3.0. I am using MRTK for building an AR experience with pass through. The passthrough does not work anymore. I am running the game on a quest pro. What is interesting, that the OVR Camera Rig Prefab that you have to provide seems to get ignored. The camera rig prefab contains the geometry for a quest2 controller. In the game I actually now see a quest pro controller. I have no ides where this geometry comes from. However it would explain why the passthrough does not work, because the OVR Passthough Layer might also get ignored. 

Do you have any ideas, where this might come from?