Dolby Vision is a proprietary format owned by Dolby - so the chance of getting it supported in Plex HTPC is pretty low. MPV - the underlying playback engine - needs to support it. Well, this is where it gets hairy. The newest build of MPV does support Dolby Vision tone mapping to SDR - but not passthrough to your TV! The implementation supports DOVI profile 5 and 8.x. (colorspace: add support for Dolby Vision · haasn/libplacebo@775a932 · GitHub) But Plex.inc is not allowed to ship this DOVI stuff due to licensing issues. (The implementation is not signed by Dolby and therefore somewhat illegal for Plex to ship it in their products).
What you can do to get Dolby Vision working is to self compile your own mpv win build or download a build here => mpv player (Windows) - Browse /libmpv at SourceForge.net
How to install => Plex HTPC feedback - #1354 by Mitzsch
