Download and save the 20.8.3 driver or the last working driver from here: Radeon™ RX 570 Previous Drivers | AMD
Download and save DDU form here: Display Driver Uninstaller Download version 18.0.3.6 (guru3d.com)
Disconnect from the internet and just use your primary display for the moment. Restart into safe mode by selecting "start", holding the "shift" key, then select "restart". A blue screen should come up, select "advanced", "startup options", the PC will reboot to a blue screen with options, select "safe mode". The PC will reboot into safe mode, install DDU and remove the GPU driver, leaving the default options alone. After the PC reboots, remain offline and install the older driver. The PC will reboot, remain offline and go into the Radeon software and disable the automatic driver update feature. Reconnect the internet and setup your secondary display the way it worked prior.
The 5000 series cards are EOL (End Of Life) so newer drivers don't contain fixes anymore for that series. They should have legacy drivers but these are sometimes unstable versions of older drivers anyway, so it's best to leave the updating off now.
"It worked before you broke it!"
