Howtoforge published a tutorial about setting up ISPConfig 3 on Debian 10/11 and Ubuntu 20.04.

Perfect Server Automated ISPConfig 3 Installation on Debian 10/11 and Ubuntu 20.04

This tutorial will take you through installing your own ISPConfig 3 single server setup using the ISPConfig auto-installer. This installer follows the old Perfect Server guides but is more modular and easy to follow. If you want to set up a multiserver setup with dedicated servers for each service instead, see the Perfect Multiserver guide.

This guide works for both Debian 10 and Ubuntu 20.04. We will use the hostname server1.example.com. Replace it where necessary.

Perfect Server Automated ISPConfig 3 Installation on Debian 10/11 and Ubuntu 20.04