"The correct behavior for devices is to treat the intermediate network between them and the servers they talk to as hostile."

Thanks for this - I had not thought of that.

Looks like I'll be keeping my "smart" TV off the network forever then (my old LG used to send a network request whenever I pressed any button on the remote)! And all my Android devices, Windows 10 devices and my Apple TV and MacBook too. (This is only partially sarcasm - I can't really trust anything these days it seems...). The amount of dialling-out they all do is astronomical. The only solution appears to be going full 1980s and not being on the network. The dream is over.

At least my Raspberry Pi can be trusted. Other than the GPU chipset...