well, good news is: it works. Bad news is, it borks my window manager. After so many attempts, I am forced to admit defeat. So, at least a few of my different methods that I tried did work, but with that comes a problem that my window manager does not want to run on my discrete GPU and then I get a bare desktop with no panels or proper windows.

Quake does launch correctly at that point but I rather have the rest of my DE actually function, and I did figure out how to set individual applications to launch on the second GPU. I'll consider this solved for my use case.... This combo of intel onboard graphics and AMD GPU was always my headache with this machine even in the times of windows.