network-manager DNS fail after upgrade with openvpn connection

[Ezequiel Larrarte]

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: network-manager 1.10.6-2ubuntu1.2
ProcVersionSignature: Ubuntu 5.0.0-37.40~18.04.1-generic 5.0.21
Uname: Linux 5.0.0-37-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Dec 28 09:42:31 2019
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2019-07-23 (158 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)

After the upgrade of network-manager, OpenVPN fails to configure DNS settings for the interface.

- List network-manager versions
# apt list -a network-manager
network-manager/bionic-updates,now 1.10.6-2ubuntu1.2 amd64 [installed]
network-manager/bionic-security 1.10.6-2ubuntu1.1 amd64
network-manager/bionic 1.10.6-2ubuntu1 amd64

- Start the connection
# nmcli connection up id VPN
Connection successfully activated

- Show connection status
# systemd-resolved --status
Link 20 (tun1)
  Current Scopes: none
  LLMNR setting: yes
  MulticastDNS setting: no
  DNSSEC setting: no
  DNSSEC supported: no

No DNS settings!

----------

- Downgrade network-manager to previous version
# apt install network-manager=1.10.6-2ubuntu1.1

- List network-manager versions
# apt list -a network-manager
network-manager/bionic-updates 1.10.6-2ubuntu1.2 amd64 [upgradable from: 1.10.6-2ubuntu1.1]
network-manager/bionic-security,now 1.10.6-2ubuntu1.1 amd64 [installed,upgradable to: 1.10.6-2ubuntu1.2]
network-manager/bionic 1.10.6-2ubuntu1 amd64

- Restart network-manager
# systemctl restart NetworkManager

- Start the connection
# nmcli connection up id VPN
Connection successfully activated

- Show connection status
# systemd-resolved --status
Link 21 (tun1)
  Current Scopes: DNS
  LLMNR setting: yes
  MulticastDNS setting: no
  DNSSEC setting: no
  DNSSEC supported: no
  DNS Servers: 10.0.0.129

DNS settings OK!