Salix OS

Is Uncomplicated Firewall more than good enough, or would you guys ultimately recommend something else as a final solution?

I use ufw, and I suspect that it's more than adequate for most circumstances, although I am not at all knowledgeable about network security. You probably don't want to be messing with iptables ... unless you already know that you really do

There is a graphical frontend for it which I gave up on packaging a Salix version or two ago, which is very user-friendly. However, there is a SlackBuild:

http://slackbuilds.org/repository/14.2/network/gui-ufw/

I also use ufw, although Eric's firewall script builder is used by many as well.
re ufw: https://docs.salixos.org/wiki/Setup_basic_firewall

re firewall script: http://www.slackware.com/~alien/efg/

Thanks guys. I'll stick with ufw as it's simple and it works. From your answers, I don't think it is any better or worse than IPtables.

Will the gui slackbuild be updated by sourcery, or will I have to maintain it manually?

There's no need to use the latest version. It's just a graphical frontend for ufw. Indeed, it isn't the latest even now - both the Slackbuild maintainer and I found that to be more trouble than it was worth.

duly noted. sticking to terminal.

IMO ufw is pretty terrible. Better use that firewall on the router.

I don't have a router.