No matter what I do, not matter which drivers I use the ONLY way to get HDR to work in this is to disconnect and reconnect my monitor cable. If I launch the game without HDR enabled and put it in exclusive fullscreen I still have to unplug and re-plug my monitor to get an image. Might add that no other games behave this way. HDR-capable or not.
Geforce drivers 417.35
Win 10 1809 (same thing happened in build 1803)
HDR disabled or enabled in Win doesn’t matter