Along with the Bestseller, Ubuntu Linux Fundamentals, Basic Linux Server Administration, two other courses are available on

pfSense Fundamentals, Secure Your Network With pfSense is a course demonstrating the most commonly used features of the open source pfSense firewall.

If you want to focus solely on learning how to securely configure Secure Shell connectivity with your Linux servers and network devices, check out Secure Shell Fundamentals – Learn SSH By Configuring It.