Passthrough broken in v66/67 VRPreview

With the current Quest 3 firmware v66/v67 passthrough is broken in VRPreview, it is drawn on top and occludes all 3D content (passthrough layer "underlay"). Even the Meta PTSamples project isn't working anymore.

Unreal Engine version and Meta plugin version do not seem to matter, the problem appeared with both setups:

UE 5.3.2 and Meta v62
UE 5.4.2 and Meta v66

Is it just me?
Is it possible to revert to an old Quest firmware?

Thank you