If you are using KDE Plasma, then you should be able to install firewalld or ufw for the firewall, and plasma-firewall for having GUI firewall settings on Plasma settings.
If you dislike plasma-firewall, then nothing beats gufw as a frontend for ufw.
Okay thanks. Would gufw be installed alongside ufw?
Nope, they are separate packages. Although installing gufw would trigger the install of ufw for obvious reasons.
I'm a big fan of firewalld with firewall-config. It's fairly easy to use even though it might look a bit complicated.
You find your default zone, usually public, you add your ports or your services, you save the changes to runtime and permanent config and you should be good to go.
There is a firewalld GUI that is pretty standard on many distros. (Fedora, opensuse, redhat, etc... use it)
Debian is a free operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run. Debian provides more than a pure OS: it comes with over 59000 packages, precompiled software bundled up in a nice format for easy installation on your machine.