That is a question that needs quite an extensive answer.
I assume that you want to know how to discover functionality on your computer in general and what strategy to follow to accomplish that, by using portforwarding as an example.
(If I'm mistaken about that, please let me know)
Port forwarding assumes that you know that you need a firewall.
Ofcourse this is on Ubuntu done by 'ufw' and 'gufw'.
If you want to know how to use 'gufw', open the manpage:
Which, aside from the regular stuff, shows a link to a 'quick setup' page:
But suppose that you don't know about ufw or iptables and want to discover for yourself what your system has to offer.
You can use this steps to get what you need to get going.
This is roughly the same for every functionality or application that you want to findout about.
1. from the terminal
The 'apropos' command returns anything it deems appropriate as answer to a random keyword. In this case 'firewall'
ufw (8) - program for managing a netfilter firewall
To see if it exists on your system:
apt search ufw
Full Text Search... Done
gufw/jammy,jammy,now 22.04.0-0ubuntu1 all [installed,automatic]
graphical user interface for ufw
plasma-firewall/jammy 5.24.4-0ubuntu1 amd64
Plasma configuration module for firewalls
ufw/jammy-updates,jammy-updates,now 0.36.1-4ubuntu0.1 all [installed,automatic]
program for managing a Netfilter firewall
This shows you the components you need and even if they are installed or not.
Also read the manualpage:
and search for rule syntax.
(in man pages the searchcommand is a slash)
the 'Search again' command is just a bare slash
instead of entering the rules in terminal, you might want to use a graphical frontend for ufw.
'apt search ufw' has shown that 'gufw' is the graphical frontend.
If it is not already installed, you might want to do so.
2. Another way is to install synaptic.
This packetmanager is perfect to do random searches for needed functionality. Use the search function to search for 'firewall'
3. The best way is to 'get' how the underlying Linux system is structured
A good overview and considered a standard work is this book:
Linux in a Nutshell, 6th Edition [Book]
Which will let you discover that 'iptables' is the base of practically all firewalls.
The desktop part ( MATE ) follows the freedesktop.org guidelines c.q. standard. You can find more about it here:
On Linux in general, all system/systemwide configuration files can be found in files and folders under '/etc/'
user configuration files for installed applications on modern desktops should be found under "$HOME/.config/" (freedesktop.org guideline)
older applications sometimes put their user-config as hidden file or folder in "$HOME"
I think that's about it in a nutshell.
I don't know if this answers your question.
Let me know, ok ?
EDIT: I almost forgot -> Books | Ubuntu MATE