Installing L2TP/IPSEC Client

Hi, I have found many different instructions, neither of which was very recent. For example:

sudo apt-get update
sudo apt-get install network-manager-l2tp
sudo apt-get install network-manager-l2tp-gnome

or

sudo add-apt-repository ppa:nm-l2tp/network-manager-l2tp
sudo apt-get update
sudo apt-get install network-manager-l2tp-gnome

or

sudo add-apt-repository universe
sudo apt update
sudo apt install network-manager-l2tp-gnome

All of them seem to reference Gnome, which is probably wrong when using Lubuntu. Anyone knows the correct instructions?

OK, so this

sudo apt update
sudo apt install network-manager-l2tp
sudo apt install network-manager-l2tp-gnome

seems to install it. But while it now shows among the connections and can be configured, there doesn’t seem to be any way to actually tell the system to connect to it. Clicking on the connection:

lubuntu-l2tp-listed
immediately results in the following message:

lubuntu-l2tp-wont-connect
Even though it was never connected to it in the first place. Both right- and left-click produce the same result. No attempt at connecting is actually made.