Can't get accurate colours in Windows HDR mode?

When Windows 10 and 11 is operated in HDR mode (HDR enabled in screen settings and outputting to a monitor expecting BT.2020), Lightroom (cloud) does not display colours accurately. It seems it colour-corrects twice - the colours look like photos were converted to BT2020 colours, then mis-tagged as sRGB and then displayed to a colour-managed BT.2020 monitor. It's probably not what happens but it looks like it - everything is super washed out. 

I tried checking "use legacy colour management" tag in Windows compatibility settings for Lightroom shortcut, and it helps to an extent - the colour saturation is normal in large image views (still off in thumbnails, but in a different way) but the colour temperature is shifted to blue everywhere. 

Windows is set up with a monitor colour profile assigned as BT.2020 Reference. This produces accurate colours in many other applications, including Chrome, for example, so it is possible (it's also possible to play HLG video files on Windows, despite Lightroom saying that Windows does not support HLG - even Window's standard Movies app has no issues doing that, but that's a separate deficiency). 

What do I need to do to make colours in Lightroom accurate in HDR mode? I know HDR is not for photos, blah-blah, but it's very common to use still images as part of a video work, and video is increasingly moving towards HDR or at least BT.2020 colour gamut.