Setting up an OpenVPN server on my Netgate SG-3100 router was a piece of cake thanks to the pfsense GUI, but seting up the Ubuntu client requires sadly still the command line.
OpenVPN
sudo systemctl start openvpn@client
The "client" is derived from the configuration file name (/etc/openvpn/client.conf). If your configuration file is server.conf, the command needs to be
sudo systemctl start openvpn@server
When you want the service to start up automatically during system boot, you issue:
sudo systemctl enable openvpn@server
Templated versus non-templated services
I just switched back from MacOSX to Ubuntu for work. Mostly for financial reasons. We need more computers at work and a really good PC laptop is just half as expensive as a MacbookPro or iMac.