i have installed 188.8.131.52 beta server in my xpenology, and the hardware transcode for hevc hdr 10bit works great!
but i found some color difference between emby player and potplayer with madVR filter in my acer SDR 4K monitor.
emby's color is actually GREY, and madVR's color is mostly like the original color in my iphone X HDR supported screen.
so from my point i suggest you could do some Color processing like madVR's doing when transcode a HDR movie to SDR playback.
emby player.png 605.34KB 3 downloads
this is emby's picture
potplayer.png 587.53KB 2 downloads
and this is same movie played in potplayer views.
infuse pro.PNG 460.24KB 2 downloads
this is played by iphone X with infuse pro. the true HDR picture.
madVR settings.png 234.86KB 3 downloads
here is my madVR's settings, convert HDR color content to SDR by using pixel shader math. if i disable "preserve hue" option, then i will get a picture almost like emby's picture.
madVR official site: http://www.madvr.com/