Heiman smoke detectors Zigbee version

This was to be expected. Which model did you buy?

Johan Bendz, the developer of the Tuya Zigbee App, is still active. Please search and use the related topic:

That is indeed the case. Most of the apps were programmed by private developers in their spare time. If you have programming skills, you can program your own apps or support the other programmers. Even a small donation supports and motivates the programmers. But even that is no guarantee that the app developer will remain active for the next 5 years, for example.
Of course, you can also send Athom (not Homey!) a request if they are willing to program an app. But I assume that Athom don’t have time and manpower for it.