OculusXR Passthrough Layer

Hey,
To me the most simple implementation of the Passthrough functionality, namely having the Passthrough layer as scene reproduced passthrough works both in Overlay and Underlay.

Has anybody tried th surface-projected passthrough? When I try, it simply does not work. I have added geometry to the passthrough layer as described by the Meta docs, but the passthrough rendition does not appear over the mesh.
Any experience?