Yep, no much result on the web about this subject.
I don’t know what the cause, nor why Sophos didn’t take it seriously.
Anyway, if you’ve downloaded version 16 of Sophos XG virtual appliance for KVM and you got the nice error message of
firstboot failed: swapon /dev/swap
But, if you know and sure you’ve done everything right and as per Sophos documents, then most likely you have the same issue we run through.
For some unclear reason we were able to solve this by having the Hyper-V version of the same appliance and run it on KVM platform :)
Our team members are testing it now on OpenStack with our service provider to make sure of the compliance.