Sudo apt-key adv -keyserver hkp://:80 -recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EFĮcho 'deb vs-bionic main' | sudo tee /etc/apt//mono-official-vs.list Ubuntu 18.04 (i386, amd64, armhf) sudo apt install apt-transport-https dirmngr Note: the packages should work on newer Ubuntu versions too but we only test the ones listed below. The package repository hosts the packages you need, add it with the following commands.