I play hdr on/off and it's the same on destiny 2. I have yet to try it on red dead redemption two. On my hdr tv on playstation hdr supported games, I tried hdr on and off. And the difference is like... An entire different game altogether. I can literally see things that I could otherwise not see. It is a different world. And a world of difference. But I have not much knowledge about what hdr does or how it exactly works. So how come stadia looks the same in hdr on/off?
For me, HDR off made a huge difference in the dark sections/scenes of Destiny 2. I could not see a darn thing with it on. My older eyes probably don't help either, ha... I normally leave it on for everything else, besides Destiny 2.