apt install apt-transport-https gnupg2 ca-certificates gpg --no-default-keyring --keyring /usr/share/keyrings/tpokorra-mono-keyring.gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0x4796B710919684AC echo 'deb [arch=amd64 signed-by=/usr/share/keyrings/tpokorra-mono-keyring.gpg] https://download.solidcharity.com/repos/tpokorra/mono/debian/buster buster main' >> /etc/apt/sources.list.d/tpokorra-mono.list apt update apt install dh-xsp