Hi, I've got Sapphire Nitro+ RX 580 8 GB with Ryzen 3900x on Asus x570-p board. I have two displays set up as Clones (I big screen Samsung TV for couch gaming and smaller Asus PC display on a workdesk for work). Currently on 20.5.1 but 20.4.2 and 20.4.1 had the same issue.
The issue: when both TV and monitor are connected (HDMI with new, fastest cables available) AND the primary (TV) is turned off, the secondary (monitor) always eventually (not immediately!) starts blinking in a ta-ta--taaa cadence. The only fix is to either unplug the TV hdmi cable or turning it on. Unplugging the TV sucks because it always scans for a "new device" after replugging, removing custom settings and stuff.
I tried various combinations of HDMI, VGA, DVI cables, various "fixes" from youtube (uninstalling iCloud, leaving Radeon settings as Standard, removing drivers with DDU, reseating GPU or installing in the other PCI slot...), none of it helps.
Weird thing is, only Windows does this. Linux as well as Hackintosh never have any blinking issues, so this is probably a software thing.
Any tips? Thanks!