You’re supposed to be able to press the Win button on your controller and bring apps into VR with you.
In MSFS 2020, if I try to open my desktop/chrome/edge/whatever, the screen flashes black for a moment, and then I get a blank window in VR with me. The FPS is 0.5 or so, and my main monitor is black and I have to reboot the computer to get back to a usable state.
Solved: Apparently having my LG OLED plugged into my 3090 (along with monitor and G2) causes irrecoverable black screen trying to open windows in VR.
I have a thread here that talks about this to a small degree.
I have had hit-or-miss luck using the WMR App Slates. Seems 1 in 5 apps will run in a Slate, with fewer than that running in a Slate from inside FS2020.
Most of the apps I’ve tried exhibit the behavior you describe, they open for an instant then disappear.