After thinking a bit about how to resolve this issue completely, I came to this conclusion:
The issue is definitely neither the game itself nor the OS (meaning Windows 10 or 11). It also can't be a CPU, RAM or whatever hardware failure/complication on my side because the game runs without crashes when using Radeon Vega 8 instead of GTX 1650. I can't blame nVidia for this because it's an eleven year old game which has been cut off from most platforms, and if it is a general GDDR6 issue, then it won't be the manufacturer's fault.
Now, we only have DXVK left. And like I said before: The game runs stable when using integrated graphics, which doesn't need the wrapper for anti-crashing. I wrote an issue to the developers which has been removed and was probably never thought about again. I'll give them a second chance, first using their tool to read out errors when the game is crashing, and send everything to them. More information to follow.