Yes, just download the mpv.dll here => mpv player (Windows) - Browse /libmpv at SourceForge.net
extract the mpv-2.dll put it in the root dir of plex htpc, rename the orig. mpv-1.dll to something like mpv-1.dll.old and then rename the mpv-2.dll to mpv-1.dll. Keep in mind you need to disable secure connections in plex htpc (plex uses the -tls_verfify setting, the ffmpeg lib is built without gnutls - I´m currently trying to get it in, so secure connections work) and you are good to go.
#EDIT: they will also work with secure connections. You need to manually specify where the cacert.pem is. Put tls-ca-file=C:\path\to\cacert.pem inside the mpv.conf and it should work.
