HDR always on in game despite PC, monitor, and game settting set to "off"

Having the same problem you are. In my case, it's persisting even after the game is closed and the only way I can get it to turn off is by restarting my PC or reinstalling Nvidia drivers.

The HDR option in-game, in Windows, and in the monitor's settings are all HDR = OFF.

If you find a way to get around this, please let me know. I've tried just about everything I can find documented to keep the game from enabling it and absolutely nothing has worked yet. It's come down to sheer luck on launch that HDR doesn't forcively enable itself.