As brew linkapps is now deprecated, the correct way to do this is to use the --with-bundle option when installing mpv.
brew install mpv --with-bundle
Because you said you have mpv installed with brew already, it's better to uninstall mpv first with
brew uninstall mpv --force After that, run the installation command above.
When the installation is finished, go to your mpv installation folder:
You will see an mpv.app in there. Right-click mpv.app > Make Alias. Copy/move the mpv.app alias into your Applications folder. Remove the 'alias' from the filename, so you'll have "mpv.app" in your Applications :)
Reference: mpv formula in homebrew's repository -
I prefer using --with-bundle rather than cask install as it allows me to use more compile options and to install different versions of mpv (e.g. --HEAD) as opposed to the pre-built package that cask install uses. Hope this helps!