i use an LG TV with 2160×3840, connected to a mac pro (late 2013) via a club 3d mini displayport 1.2 to HDMI 2.0 active adapter.
worked like a charm in sierra, 50Hz or 60Hz for 2160×3840.
after update to high sierra, max frequency is 30Hz. picture quality is slightly lower than before, eg color edges on small letters. system profiler says 2160×[email protected].
any ideas to get 60Hz back?