digiKam 6.3.0 seems to running stable… As long as I don’t select a fresh ‘collection’ e.g. a directory which has not been scanned before by digiKam.
As soon as I add a new Local Collection, digiKam starts processing this, you can see the progress bar/percentage increasing at the bottom of the screen.
But when I move the mouse cursor around and try to select any existing Album, I don’t get any response any more and a few seconds later, digiKam crashes… 
Just before the mouse cursor changed into the hour-glass symbol.
[additional info]:
Any action, while digiKam is processing (?) a freshly added ‘collection’ results in the hour-glass mouse cursor and no response anymore from digiKam. And once clicked anywhere in the Album window → crash.
You will have to wait until processing has finished; only then digiKam does respond and no crash anymore. But this is very cumbersome.
With the same error message in the event log.
Faulting application name: digikam.exe, version: 0.0.0.0, time stamp: 0x5d6fdfed
Faulting module name: Qt5Core.dll, version: 5.13.0.0, time stamp: 0x00000000
Exception code: 0xc0000602
Fault offset: 0x000000000032bfe1
Faulting process id: 0x2518
Faulting application start time: 0x01d582d69971b7d8
Faulting application path: C:\Program Files\digiKam\digikam.exe
Faulting module path: C:\Program Files\digiKam\Qt5Core.dll
Report Id: e4d45037-0681-4e38-91f7-5f3fa53aca15
Faulting package full name:
Faulting package-relative application ID: