Ubuntu
Jammy Focal Bionic Xenial

curl -fsSL https://repo.serverforge.org/repo.serverforge.key | sudo apt-key add -
sudo add-apt-repository "deb http://repo.serverforge.org/ focal main"

Debian
Bullseye Buster Stretch Jessie

curl -fsSL https://repo.serverforge.org/repo.serverforge.key | sudo apt-key add -
sudo add-apt-repository "deb http://repo.serverforge.org/ buster main"