IoT works just fine with Zigbee that can be 100% local.

Most of which you don't need IMO. When a bunch of stuff had to be redone after a kitchen fire, I told my electrician that I wanted everything to be dumb.

Did IoT cause the fire?

No. A 15-year old (so not ancient) dumb microwave.

Not a luddite but, aside from a couple of Alexas, just no need for any IoT.

How did you start a fire with a microwave? Plain old electrical fire, rats eating wire insulation?

Apparently a short circuit in the control panel in the middle of the night. At least that's what the investigator said. I wasn't using it and was asleep. So I didn't start it. Was spontaneous. Didn't seem to be related to any external wiring.