This is on the latest released version of MSFS 2020 on a rig with an AMD 35something processor and a RTX 3090 card. I am using the replacement cable with the switch and the electronic within it that resolves issues with the AMD usb controller (which it does).
Originally the screen on the Reverb G2 would go dark for more than one reason. One was that the USB audio driver crashed and got reloaded by windows. The Reverb will display a dark screen and a speaker icon that shows changes to the volume of the speaker but will most often recover eventually. This issue had been reported long since and apperently has been resolved with the replacement cable. If your G2 is within the warranty period you get it for free. But the Reverb may still black out occasionally after installing it. This time without displaying the speaker icon, it simply goes dark and stays there.
The reason as I experience the issue seems to be related to the logic Windows uess to dertermine wether to put the Reverb in standby and/or switching input between WMR home and MSFS. As every time the Reverb goes black for me while flying in the MSFS, entering Win + Y two times will recover it. There is an possibly unrelated issues after that: the mouse cursor disapperead and you need to switch out of VR and in again to recover that. As the initial placement of the cursor looks like being far beyond anything visible and one can get it closer only within WMR home, not MSFS.
I am running this with the standard WMR settings on W10 (most recent patches and rollups applied to the OS and all sofware running on it). Turning off the setting to detect standby conditions or the setting to switch input seem to make things worsem i…e. the blackout happens more often then. I tried installing the OpenXR dev tools and activiating the most recent beta OpenXR driver but that again worsened things. Every attempt to remedy the thing resulted in more frequent blackouts.