In the fix for
QTBUG-74317, a change was made to use a "presentable" name for each display instead of the previously generated name (which happened to be unique for each display). This causes a problem because QWindowsScreenManager::handleScreenChanges() treats the items in newDataList as if they are the same physical display if they have the same name.
The upshot is that if you have multiple identical displays connected to your machine, Qt will see those as only 1 display. This results in weird behavior, such as that I reported in
I have attached the relevant output from qtdiag.exe version 5.15.3 and 6.2.4.