Best way to install is using official docs from osx repo here. Remember to configure meld as difftool in the command line as well.
There are two ways of installing meld on osx, using brew and .dmg package (from @yousseb). Since I found https://yousseb.github.io/meld/, I've installed it with .dmg package, but having macOS Ventura Version 13.4 (22F66) in place, it's not even starting for me. So I tried brew installation, and the application is working as expected, including symlink to start it from the terminal.