I have the exact same issue with my sapphire r9 270x vapor-x like avnrv. After the last windows update and the Adrenalin updates the card became useless - black screen on boot and during install of at least 5 different versions of Adrenalin software like 19.2.3, 20.3.1, 20.4.2, 20.5.1 (with Clean restet) and even after DDU in safe mode.
Motherboard Gigabite 990XA-UD3
AMD FX 6300
Sapphire Radeon R9 270X Vapor-X 2G OC edition
Windows 10 Pro 64 bit
With Microsoft Basic Display Adapter it runs without any artefacts, even Heroes III runs perfectly and 1080p videos. But still nothing after multiple times to reinstall the drivers and this cannot be that bad... The PC cannot be used for more serious games because of the drivers issue, as it crashes right away when installing and please advise as multiple people have reported similar issues with the 270X cards.