No help from GMG. Got it- don't ever pre-order from them. Lesson learned.
HDR seems to be fucked on my primary display now. It's possible the latest nVidia update broke something, but I'm blaming the game since it's way too much of a coincidence that it happened right when I tried to toggle HDR off in game.
Can at least get back to normal now on the monitor if I change the refresh rate to 60hz, turn hdr off, then I can go back to 240hz.
Game uninstalled. Oh well, maybe in a few months it will work?