Does each power connector on your GPU have it's own dedicated power cable that is not being shared with any other device and do not use the pigtail connections that come on PCIE 8 or 6 pin cables.
AMD GPU's can be very finicky when it comes to uneven power distribution.
Try moving the PCIE power cables to different ports on your PSU if you are running a multi rail power supply.
Also ensure that the HDMI or DVI cables going to your monitors can handle at least 50% higher FPS rates than you use.
I have found that using the AMD chill feature where you lock in max and minimum FPS helps avoid black screens and crashes that come with them.
I'm running a Power Color Demon RX 6900 XT and used to experience this same issues after I installed my GPU. I was using one of the pigtail PCIE cable connections. Since I changed that and use AMD chill in Adrenaline the problem hasn't returned.
My monitor is a ViewSonic 50" UHD 4K Smart Monitor. Standard FPS at 4K is 120Hz at lower resolution it runs up to 240Hz.
Yes when I experienced the black screens the only way to recover was a Hard Boot as well.