(not to be confused with the excellent application by Guy Godin!)
In some laptop configurations, the virtual desktop button seen in the Rift dashboard (or when using the Quest with Link or Air Link) produces a black screen. This is somehow related to the GPU (integrated or discrete) being used.
This is how I got it fixed:
Go to Windows Settings -> System -> Display -> Graphics Settings (way at the bottom).
Under "Graphics performance preference" -> "Choose an app to set preference" -> "Desktop app".