Another item that could help anyone else that stumbles upon this thread, as it helped me, was to make sure that the OpenXR driver is installed on the Windows machine. I had to download the one for Windows MR and on the third tab, had to install the driver once more. Then go into the Oculus Desktop App settings, then the General tab, and make sure that the Oculus device is set to the Active OpenXR Runtime.
Doing this, I was able to fix my issue with having the “Preview in VR” item being greyed out.