Now it’s not necessary anymore to use a special installer to install SMPlayer with mpv. The regular installer gives the possibility to install either mplayer or mpv.
Just click on “Playback components” and select mpv. An mpv build will be downloaded from the internet, so you need an internet connection to perform the installation.
If you don’t know what mpv is, please read this previous article:
SMPlayer with support for MPV is now available/