Like most of you here, I also had the intermittent black screen and been watching very closely all the diagnosis tips on this forum and others on Reddit.
I noticed that there is no consistent trigger for the black screen (ie there is no one thing that I do/not do to trigger the black screen. I can at time see the start up Mixed reality house, and then a few seconds later the VR goes black. I did not move my head nor did i touch the cable).
That alone suggests to me that it is not a software issue (not FS2020, DCS or any other game) but hardware, and most likely the cable (i’m on my 2nd HP Reverb G2 cable. Had the original one which we all know to be faulty, and got a free replacement cable from HP some 2 years ago, which has been working fine until about a month ago when I started to experience the black screen.
Anyway I did not want to buy a replacement cable as it is very costly and end up finding that the cable is not the cause of the problem.
So, I reached out to HP support, and explained the problem to them. Initially they were happy to SELL me with a replacement cable since my warranty had expired some 2 years ago.
I asked that they reconsider given the high price we paid for the HP reverb G2 and the known problem history of the cable.
The support rep agreed to raise a ricket and escalate the issue to 2nd level support with my request.
To their credit, 2nd level support called me within 2 hours, and after explaining the problem to them they agreed to send me a replacement cable FREE of charge.
A day later (this afternoon) I got the replacement cable and the VR worked with not 1 instance of a black screen.
So in my case the faulty cable was the cause of the problem. Specifically, its the display port plug that goes into the headset is the culprit.
Think I may buy a second cable just in case.