The game is NOT using/applying Xbox, Playstation or PC HDR Calibration app settings.
Unfortunately the game is native SDR only and its default in-game SDR setting provide a slightly raised picture which can be partially improved with a small change.
For all TVs/Displays,
Decrease the Brightness Intensity slider to -1 in order to mitigate the raised blacks without crushing details
Once you've adjusted SDR, you can then just use RTX HDR on PC to have a good "simil-native" HDR presentation.
Unfortunately the game doesn't support AutoHDR on Xbox for some reason, which is a shame...
BONUS:
On Consoles: use the Performance graphics mode for much smoother gameplay, even if you will have some visuals cuts and VRR is recommended as 60fps won't always be locked
On PC: go have a look at my optimization mod for it (which still is the #1 mod for Oblivion Remastered on the entire Nexusmods! ❤️)
Enjoy! :)
-P