@tickmike, @7LM - so given that my wife is on an EE contract, and has an iPhone, then in theory wifi calling ought to work?
Janet’s iPhone connects to the house’s wireless LAN fine as I can ping it using its A&A static IPv4 WLAN address, and my Firebrick router can see the iPhone, lists it on the list of DHCP clients and in the known ARP list. (Each known host gets an IPv4 address via DHCP, but that address is actually constant, set according to a long list of MAC address -> IPv4 mappings in the router.)
I read tickmike’s very helpful old post about the EE/Cisco boxes. Do I actually need one though given that this Apple phone does supposedly speak wifi calling?
I could start either by talking to Apple or by talking to EE - nightmare, each will blame the other. I will recheck the settings yet again, but I should probably get Apple to help me with that.