SUMMARY, STEPS TO REPRODUCE, AND OBSERVED RESULT
1. In a Live Session, System Settings doesn't show Firewall as "Enabled", but after a fresh install of KDE neon using my /home partition (from Kubuntu), System Settings showed it as "Enabled", although the output of terminal command "sudo ufw status verbose" said it was inactive. However, entering the command "sudo ufw enable" in Konsole, followed by commands to open ports for KDE Connect, properly resulted in 4 rules being displayed in System Settings.
2. Systems Settings also shows Firewall Default Incoming Policy as "Ignore" (and not "Reject"), although the output of terminal command "sudo ufw status verbose" is "Default: deny (incoming), allow (outgoing), disabled (routed)".
1. The status of Firewall in System Settings should at all circumstances match the output of the terminal command "sudo ufw status verbose".
2. Default Incoming Policy should be "Deny" and not "Ignore" (also using the term "Deny" instead of "Reject" for the sake of terminological consistency).
Operating System: KDE neon 5.21
KDE Plasma Version: 5.21.3
KDE Frameworks Version: 5.80.0
Qt Version: 5.15.2
just tried on a firewalld system with `firewall-cmd --state` and got the correct result FWIW.
(In reply to Nate Graham from comment #1)
I also tested this again on a completely fresh install, and I couldn't reproduce contradictory firewall status information. Probably it was one of those one-off things that can be ignored.
I cannot say much about the Default Incoming Policy being reported "Ignore" (and not "Reject") in Plasma Firewall Settings, although it is "Deny" according to the output of "sudo ufw status verbose".