packages.icinga.com (Icinga2)

apt update
apt -y install apt-transport-https wget gnupg
wget -O - https://packages.icinga.com/icinga.key | gpg --dearmor -o /usr/share/keyrings/icinga-archive-keyring.gpg
DIST=$(awk -F"[)(]+" '/VERSION=/ {print $2}' /etc/os-release); \
 echo "deb [signed-by=/usr/share/keyrings/icinga-archive-keyring.gpg] https://packages.icinga.com/debian icinga-${DIST} main" > \
 /etc/apt/sources.list.d/${DIST}-icinga.list
 echo "deb-src [signed-by=/usr/share/keyrings/icinga-archive-keyring.gpg] https://packages.icinga.com/debian icinga-${DIST} main" >> \
 /etc/apt/sources.list.d/${DIST}-icinga.list
apt update