Geez... I mind as well give this up.. I don't understand any of these...
I've scanned the whole range of ports (as you've suggested in that topic) and it's not responding. Could it be one of these settings on my router?
Also known as "Virtual Servers" in the submenu of your screenshot. Welcome in the world of Network Address Translation. It's not difficult, in fact it's pretty easy and logical. And no range needs to be scanned, only the game port defined @LFS setup.cfg .. You can do this, I am sure
Amazingly, I've managed to do all the steps (change to static IP and open the port)... will test it in the afternoon if it really works and let you know.