Add repository and install the Updater

Install HTTPS transport

apt install apt-transport-https

Note: this package might already be installed

Import key

curl -fsSL https://packages.cisofy.com/keys/cisofy-software-public.key | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/cisofy-software-public.gpg

Configure the software repository

echo "deb [arch=amd64 signed-by=/etc/apt/trusted.gpg.d/cisofy-software-public.gpg] https://packages.cisofy.com/customers/LICENSE/lynis-enterprise/deb/ stable main" | sudo tee /etc/apt/sources.list.d/cisofy-lynis-enterprise.list

Important note: replace LICENSE with the actual master license key.

Update repositories

apt update

Install the Lynis Enterprise Updater

apt -y install lynis-enterprise-updater