Did you create a monitor profile specifically for the HDR setting?
Your screen capture does not show the navigator panel, nor, more importantly the Histogram. Is the histogram also wonky?
No, the histogram seems to be ok.
Other people have found that turning off the HDR fixes this problem in Lightroom Classic. Even though you say "except from turning off HDR...", that seems to be the solution. (And really, you don't need or want your monitor's HDR on when using Lightroom Classic).
This is the correct answer. You don't want your monitor in HDR mode when working with digital images. HDR for images is very much still a gimmick with no agreed upon format or standard.
Thank you all. I wrongfully assumed that HDR only was active when gaming.