Install Mono Offizelle Seite: https://www.mono-project.com/download/stable/#download-lin-ubuntu Add the Mono repository to your system sudo apt install gnupg ca-certificates sudo apt-key adv –keyserver hkp://keyserver.ubuntu.com:80 –recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF echo „deb https://download.mono-project.com/repo/ubuntu stable-bionic main“ | sudo tee /etc/apt/sources.list.d/mono-official-stable.list sudo apt update Mono sudo apt install