Comment 116 for bug 1624317

So the issue persists I believe. Unfortunately I just broke totally broke my installation of Ubuntu 17.04 using 'sudo make install' on the git master of NM and was unable to connect to the internet at all, so someone else is going to have to test or figure that one out. :(
I'm almost positive, however that the issue would remain. Using openvpn through network-manager-openvpn, the line "DNS Domain: ~." under the VPN link number and info with "systemd-resolved --status" is missing or has nothing after the colon. So the routing-only domain is not used for the openvpn link like tun0, and we have dns leaks. Please contact the devs at canonical assigned to https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1624317
This is a fairly critical bug that I think needs to be worked out with other people more knowledgeable there. I'm afraid I can't help much more, sorry.