This type of configuration (using a AMD GPU and a Nvidia GPU in the same system) is not supported and could well be the cause of this issue.
If the issue occurs with just an AMD GPU present in the system, please can you show this happening and follow the same steps as you followed in the video above, showing task manager and using ReLive to capture the footage.
I have the same issue. Installed the 20.2.2 driver today for my RX580, and right after reboot, the cursor starts flashing "working in background". I have no other GPU installed - only the RX580. I 've tried uploading a video here. Don't know if it worked..