As few of you might have noticed Xamarin folks have stopped updating the per distro packages for MonoDevelop so you are all probably stuck with MonoDevelop 5.9, while MonoGame requires MonoDevelop 6 for the plugin. MonoGame also won't work with the flatpak version (at least the 3.6 won't) because it has it's own content builder which is not sandboxed.
Since many of you will have problems installing MonoGame I decided to write down these installation instructions, they are split into 3 steps and if you are running Arch Linux based distro, you can skip steps 1 and 2 since Arch Linux already provides the newest monodevleop version.
1. Installing the newest possible versions official versions of mono and MonoDevelop
You can find the newest possible versions of both of those from: http://www.monodevelop.com/download/linux/, you just need to follow the Legacy instructions for your distribution.
2. Installing MonoDevelop 6
I took the time to package the newest possible version of MonoDevelop in a way that can be installed on any Linux systems, the package source can be found at: https://github.com/cra0zy/monodevelop-run-installer
To install MonoDevelop 6 simply run the following commands:
chmod +x monodevelop-22.214.171.1248-1.run
3. Installing MonoGame
Simply download and run the installer:
chmod +x monogame-sdk.run
The installer will automatically check and warn you if you are missing any dependency.