Windows 11 broke AMD RX580 DisplayPort (after 3 attempted installs)

This problem drove me crazy for a while too. It seems the AMD driver that downloads and installs automatically, changes something on the video card that doesn't revert when you reboot the PC. I'm pretty sure this is an AMD driver problem, but it could be related to how Windows 11 does automatic HDR (high dynamic range). My own theory is the driver is setting the DisplayPort output to 10 bits (HDR) per pixel instead of the normal 8 bit, or something else slightly exotic, and then the display connected to the DisplayPort can't decode the signal coming across the wire. I fixed this problem by swapping my monitors over. Both of my monitors had HDMI and Display Port inputs, so I was able to swap them over between the HDMI and DisplayPort outputs on the graphics card. One thing I noticed was my 2 supposedly identical monitors were reporting slightly different capabilities. So potentially this is a monitor problem, where the monitor incorrectly reports its capabilities, and the video card driver is setting up the graphics card to output a signal the monitor can't handle. So something to try is swapping the monitor. Also a good idea would be to turn off the PC completely, including unplugging it from the mains power for about a minute. Sometimes a sticky hardware problem requires all power to be removed before it can be rectified.