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Is SSL VPN available on
SFOS 18.5.4 MR-4-Build418
Probably something to ask on the XG forums, not UTM - but I would say that it is. It's on the product page. Sophos Firewall Management and Security Features
XG 19.5 GA 64-bit | Intel Xeon 4-core v3 1225 3.20Ghz 16GB Memory | 500GB SSD HDD | GB Ethernet x5
Yes, both remote-access and site-to-site. I use remote access SSL VPN on mine to connect when offsite.