OK . . . . Don't ask me why, but I decided to try something. The default start up starts GOG Galaxy (company I bought the game from) before starting the game. So, I went into the program and found a short cut to launch the game directly with out going through GOG Galaxy. The game works fine like this. This inspired me to try something else. I loaded the game using the default shortcut which starts GOG Galaxy. However, before starting the game, I killed GOG Galaxy. The game runs fine. Each step is repeatable on my end with the exact same results.
So, the bug is with DoS2 Definitive Edition, running fullscreen mode, with a single monitor, with GOG Galaxy running and has indications of having to do with GeForce drivers.
Good luck!! In my experience with programming if you can find the people responsible for the code in separate companies, they could likely figure in out in under 30 minutes. However, I have some experience with the industry and understand the likelihood of that happening is close to that of winning the lottery. Again, good luck!!!