Developing my first Linux program with Mono ^_^

Why not just .Net core?

IMHO mono is shit. Note that I'm talking about the IDE, not the runtime.
I code in VS and throw the binarys into the runtime. Most of the time I have to install missing libraries and fix things not supported by mono atm but other than that it works.
But you really should look into .net core if you're just getting started

If Linux clang or gcc

The newest version of mono uses some dumb new package manager that doesn't work correctly with monogame. Flatpak or something like that. Sounds good on paper but doesn't implement well.