https://github.com/OpenRCT2/OpenRCT2/issues/3940
IntelOrca linked the following Version for this error on GitHub: https://openrct2.org/downloads/develop/97fedab
With this, OpenRCT2 works.
I have one further, small question which probably doesn't need it's own thread:
Can i use saved games in OpenRCT2 without restriction in the original RCT2? And how about vice versa?
I just tried to load an OpenRCT2 save in RCT2, which worked. I'm wondering, if this works 100%, or if certain elements may be missing.