I have a BenQ BL3201PT 32" UHD display that supports 10bit color channels on Windows desktop. In nVidia control panel settings, it shows up as a output color depth 10bpc in addition to 8pbc. Here is a screenshot of the control panel setting (googled from the web, that one has even 12bpc option it looks like)
As mentioned above, agree that simply having 10bpc over 8bpc doesn't mean much, unless the actual color space that the monitor can output would increase. This BenQ does not support the Rec.2020 colorspace (or even close), since I don't see any difference in anything with 10bpc vs 8bpc, i.e. 8bpc does not produce banding, nor does 10bpc mode produce any more brightness/luminance/colors/(dynamic) contrast. The TomsHardware test confirms that the display covers only 71.84% of Adobe RGB 1998 color space (and Rec.2020 is way larger than Adobe RGB 1998), and the 10bpc mode is implemented with FRC (frame rate control), so the "supports 10bpc" label on a display is not worth much alone.
Looking forward to seeing a display first hand that would support the full Rec.2020 space. Anyone knows if such displays are actually available for purchase yet?