I too have a IOT doorbell! It's using Zigbee, just like the actual speaker ("bell") that also serves as our home security audible alarm, and other things. It's basically "Button on the outside of house > Home Assistant > Speaker", and works 100% offline, and is backed by a UPS :)
If you get rid of HTTP and 3rd party services, all this stuff gets really simple, durable and easy to maintain. Haven't touched the setup in years, except to change the battery once in the bell as it's 100% remote, haven't had a single issue since we set it up.
If you get rid of HTTP and 3rd party services, all this stuff gets really simple, durable and easy to maintain. Haven't touched the setup in years, except to change the battery once in the bell as it's 100% remote, haven't had a single issue since we set it up.