Firestarter was a package available through Debian that showed active connections (and a few other features which gufw does not have).
You could observe the log of attempts to connect and create rules to either block or allow similar connections by clicking on the log entries.
Is there a way to get this sort of functionality now that Firestarter is not in active development and no longer an available Debian package?
And are there ways to use firestarter with a VPN?
It seems that firestarter is obsolete in Ubuntu.
It was shown in pkgs.org listings - Debian 7 (Wheezy) and Ubuntu 12.04 LTS (EOL now), currently repology does not show any Debian-based distros.
Download link on official FireStarter site does not open.
But you can try to build (from this source) on 16.04 LTS ESM or 18.04 LTS:
Self-compiled firestarter launches but writes many errors and warning to the terminal.
I think there was a reason of removing it from official repositories, so you should use
gufw
.