I am having the same problem with NVIDIA GTX 1660 Super / 6 Gig VRam
Windows 10 Pro - 20H2 - OS Build 19042.985 - NVIDIA Driver 466.11
ATM, I just work on BP’s and have nothing fancy in the UE4 Viewport
and I don’t have this problem (that a menu list goes black) in any other APP or in UE4 Game’s
I will give this a try now: After updating to NVIDIA Game Ready Driver 461.09 or newer, some desktop apps may flicker or stutter when resizing the window on some PC configurations | NVIDIA
EDIT: The issue for me is finally fixed with the registry file “mpo_disable.reg” - see the NVIDIA Link below