Sophos XG v18 - SSL VPN Client with OpenVPN Connect v3

Sophos Connect should fix this issue? Could you try Sophos Connect. 

I don't use Sophos Connect it's for IPsec remote access VPN.

I doesn't have the choice I need to use OpenVPN. Office Sophos SSL VPN Client work. But I need to use OpenVPN Connect v3 for Windows.

OpenVPN Connect for Android work too, unlike Windows and macOS version.

Left : OpenVPN Connect v3 (issue with DNS) and Right : Sophos SSL VPN (work fine)

New Sophos Connect 2.0 is for IPsec and SSL VPN. Just import .ovpn or use provisioning.

I have this same issue.
We have lots of VPN clients and we have people swapping and sharing all the time. Ideally we don't want to have to add user rights to the sophos program files if we can avoid it.
Surely there must be a fix for this as both clients use the same fundamental programming from openvpn?

After some trial and error I have found the real reason for this. When you connect to the VPN using openvpn client the system doesn't put the domain prefix into the suffix of the adapter when it connects. 

I was just having this issue and found a KB where one of the commenters posted a different version of the Wintap driver. 
SSL-VPN-Client and Windows 10? - VPN: Site to Site and Remote Access - UTM Firewall - Sophos Community

Give that a try. I just installed that and it fixed my DNS issues. I've got to do further digging to see if there is an updated version that also works.