Network Manager and VPN

[TheFu]

Glad you figured this out.
ifupdown and /etc/network/interfaces has been deprecated on Ubuntu for a few years. Ubuntu moved to Netplan. BTW, Debian is **not** an official flavor of ubuntu. Would have been better to place this question into the Debian sub-forum. Seems in the LinuxQuestions link, someone with the same username as here said Debian was being used. That could have helped someone else know the specific differences between debian and Ubuntu network stacks.

For lurkers, if you have any networking issue, the first steps are to test ping using IP addresses and using DNS names. If IP works, but DNS doesn't, you know that DNS is the problem and can concentrate on that. If IPs don't ping, then the problem becomes much more complex.

I find it odd that the DNS worked from the CLI - managed by network manager, but not from the GUI network-manager. That doesn't make sense. Seems like a bug. On all the VPNs I've used and manage, we (on the VPN server side) always forced the correct DNS for every client. Clients should never need to know a DNS setting. The VPN should pass that in the connection configuration automatically and it should override any localized settings. Anything less is a bug, IMHO.