Sophos XG Firewall is described as 'A modern replacement for Sophos UTM based on Sophos, Cyberoam and Astaro technology combined' and is a Firewall in the security & privacy category. There are eight alternatives to Sophos XG Firewall for a variety of platforms, including Linux, Windows, Web-based, BSD and VirtualBox apps. The best Sophos XG Firewall alternative is pfSense, which is both free and Open Source. Other great apps like Sophos XG Firewall are ClearOS, Endian Firewall Community, Sophos UTM and Kerio Control.
one is an OS, the other is an app