Yes, there had been progress. Slicer has switched to the latest VTK master version, which supports both OpenVR and OpenXR. The SlicerVirtualReality extension works with this latest VTK version. I think it still uses the OpenVR interface, but in the mid/long term the interface will be switched to OpenXR.
In the meantime, you can use CloudXR with the HoloLens. It has been recently demonstrated to work well with Slicer and an Oculus Quest headset, and it is supposed to work rieh HoloLens, too.