Also, 10-bit support is only a part of it, these days one also has to take care of compositing for HDR (e.g. UI elements at a particular brightness level, while image surface remains unlimited…), and I don’t think anyone is quite there yet.
And yes, 8-bit vs 10-bit doesn’t really make a huge difference at 100-200nits (SDR), but it really makes a difference for >1000nit HDR displays.