I am successfully using the Gamepass version of FS2020 along with VR Desktop and an Oculus Quest 2.
Even though you don’t have the Steam version of FS2020, it still uses Steam VR. So ensure you download Steam and Steam VR.
Start Steam VR. Start VR Desktop. Start FS2020. Hit CTRL-Tab when you’re ready to switch to VR mode. That’s it!