I just tuned HDR on on my monitor and Windows OS to check.
As waltc said:
HDR in-game options only show, if the game detects that HDR is 'on' on the Windows/Monitor level (10-bit color or more or OLED screen)
With 'HDR off' in Windows, the monitor will not do HDR output (stuck at 8-bit color). And the game menu will not present the HDR option.
@Yam9543 are you running the Witcher3Remaster on Windows 7? Because 'HDR' is supported in all Win10/11, Linux and Mac OS versions. And Win7 should not work with the Remastered.