Installing MonoDevelop on Ubuntu 20.04

 To install MonoDevelop on Ubuntu 20.04/20.10, do:

$: sudo apt install apt-transport-https dirmngr
$: sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
$: echo "deb https://download.mono-project.com/repo/ubuntu vs-bionic main" | sudo tee /etc/apt/sources.list.d/mono-official-vs.list
$: sudo apt update
$: sudo apt-get install monodevelop
$: echo "deb https://download.mono-project.com/repo/ubuntu vs-focal main" | sudo tee /etc/apt/sources.list.d/mono-official-vs.list
$: sudo apt update
$: sudo apt upgrade

Note that:

• As of this writing (12/22/2020) https://www.monodevelop.com/download/ only shows support for Ubuntu 18.04
• I have only tested this on very simple application - console and Gtk2 dialog app
• You will notice that I started installing using Bionic (Ubuntu 18.04) and then changed to Focal (Ubuntu 20.04) to upgrade all the libraries
• This applies to Pop!_OS 20.10