How to connect to NOVA's VPN from Linux

Apparently, NOVA's technical department is too busy to make guides for Linux users (only Windows and Mac). Something that even the University of Lisbon has - which is funny, because NOVA's supposed to be the modern & state-of-the-art university (thus making the University of Lisbon the old & classic one).

Anyway, here is a guide for Ubuntu 20.04.5 LTS (I'm not on 22.04, yet). Might be useful for other students.

1. Get the L2TP plugin.

NOVA's VPN uses L2TP protocol, which is not available by default on Ubuntu. Open the Software Center, search for "L2TP" and the Gnome Settings will appear. In it, locate and install the L2TP plugin. Reset the computer / restart the session.

2. Configuring the VPN.

- Go to Moodle, on the right side you have some documents available, including .pdf guides to set up the VPN on Windows & Mac. Download one, as you will need information from there.

- On your computer, go to the Network settings and add a new VPN. Now you have an new option: L2TP. Choose it and fill in the fields:
Name: Whatever you like, it will be the name of the VPN connection, for your computer.
Gateway: The IP address number you can find in the .pdf guide. Ex: 123.456.789.101. (You may ask: "Why don't they use a subdomain, so if they ever need to change the IP, they don't break the configuration on everyone's computers?" That's a good question. No idea...)
Username & password: the same for netpa/moodle. You can click in the little user icon inside the password field, for options regarding password storage. Leave the rest empty.

- Click in IPsecSettings, below. Enable IPsec tunnel to L2TP host. In the Pre-shared key, use the one from the .pdf files (they call it pre-shared key or shared secret). Save.
- Now open PPP Settings. Activate end-to-end encryption (MPPE). Save.

Save the connections settings. Turn on the VPN. Done!

Note: I have my operating system in Portuguese, so some of the wording I mention might be slightly different.