Hi,
I own JRiver for a long time (several years).
I switched from Sony 65ZD9 4K TV to Samsung 75Q900R (8k / HDR / 12 bits).
MadVR shows correct identifications (3840x2160 / 8 bit/12bit bitdepths).
But Nvidia control panel only have 8bpc option (3840x2160 24 Hz - Full RGB)
My Sony has 12 bits option available.
I suspect something wrong with Samsung EDID. On Windows (display options), Samsung uses Plug &Play generic monitor.
Thanks for your help