Hi,
I recently bought a "Club 3D DisplayPort 1.4 to HDMI 2.0a HDR Active Adapter'', connected from my AMD RX580 DisplayPort 1.4 to the HDMI 2.0 port of my 43'' LG 43UD79-B which worked very well with High Sierra 10.13.5 but since I update my OS to 10.13.6 the adapter no longer support 60 Hz ,HDMI Ultra Deep Color freezing my screen if enable , 4:4:4 is no longer supported @60Hz .
I tried ResXtreme and SwitchResX without success ,I also did a reset of the PRAM and VRAM .
Same issue with my LG 55'' Oled Tv.