There are plenty of devices where this is the case. For example, the ikea devices. Generally, most HomeKit devices are LAN or Bluetooth based, and theoretical

There are plenty of devices where this is the case. For example, the ikea devices. Generally, most HomeKit devices are LAN or Bluetooth based, and theoretical should work without needing to phone home. (Some might stop if they can’t, but that’s an implementation issue, and i haven’t experienced it yet)