Bug?
After updating to Radeon 21.4.1 released on 13/04/2021 my primary monitor was acting strangely and now displaying applications.
I found that the reason was that my HTC Vive headset was automatically registered as primary display. Prior to this update, it was plugged in and remained on standby. This has never been a problem before and I have made no changes between updating Radeon.
This is now registered as an additional monitor and forces an extension to my display which I do not want.