Local IP connectivity to router apparently dead while WiFi still working

Good sanity testing fundamentals, thank you, although I have fixed this. I believe that I have revealed what can be used to diagnose the exact problem in this upgrade.

Repeated resets, repeated FW upgrades to the latest all achieved nothing. But, I immediately restored settings everytime, as per sensible guidance here. It should not have been a problem, but it was. This 'restored' the problem that the firmware introduced. This begins to make the problem isolatable by Netgear.

So, I manually created my complex DHCP fixed structure and my SSID details. And it works now. Between devices and Orbi units. I should not have to do this.

This means that something in the configuration structure does not port well between these firmware versions. I presume it has something to do with routing/iptables that this new App Armor thing has poorly implemented, regardless of whether it is enabled(!) (I do and did not have it enabled).

None of this is good news. I have two ruined days. And I would be irrational to trust my Netgear equipment. The scenario if I were travelling would be worse. If you have a NAS, an inward VPN, CCTV, alarms, Ring doorbells, Arlo or are just a modern user, you cannot trust a system or manufacturer that will destroy your network whenever it wants.

I am furious.