If they do the object recognition on the cloud there is no way they offer those doorbells without any monthly subscription. My guess is that it is either doing something on the device or is just a dumb camera with an RTSP feed without any AI features.

My guess is the latter, considering the price. And still 20 bucks for this doorbell without a monthly subscription is a good deal. If they build something natively supporting Home Assistant that would be a killer device.

But as a friend used to say, if something is free, you are the product.