Simply put, I managed to open an Age of Empires II room in GameRanger without leaving my MacBook Pro with macOS Mojave (which I use for daily use).
I use this to see if there is someone around who wants to play.
In order to play a game I still have to turn on my iBook G4 and start GameRanger etc. there, though.
But that’s cool! I can open an AoE-II room from macOS Mojave!
You need the Age II executable 1.0.6 version, then you have to add the “game” to GameRanger.