I just noticed that the Plex HTPC auto update also removed the added mpv.conf file.
I re-added GitHub - hl2guide/better-mpv-config: An improved MPV Media Player v3 configuration file. with the addition of “tls-ca-file=C:\Program Files\Plex\Plex HTPC\resources\cacert.pem” as per [HDR Metadata Passthrough] - Plex HTPC for Windows
Not sure if there are any other recommended Plex HTPC specific configurations that are ideal to get highest quality video and audio playback?
I think I will see how often auto-updates happen and look into writing a script to auto copy/replace from a directory to Plex HTPC if frequent manual replacing is required.
It would be awesome if Plex automatically included an MPV-2.dll + mpv.conf that resolved this issue and included ideal default configuration for maximum quality on playback of HDR/EAC3/4K/H265 etc content. – maybe dynamically altering the mpv.conf based on hardware detected on install.