There is an active discussion of how to bring ST into HomeKit once the Groovy cloud is gone in the following thread, but it’s over 300 messages down from the start of thread. I’m starting this new topic so the discussion is easier to find.
There are a couple of different possibilities detailed there. For example, one uses MQTT as an intermediary, another uses Home Assistant. A third is a regular Homebridge plugin and a fourth by the same author is a plug-in specifically for HOOBS.
(Since Samsung has said officially that ST hubs will NOT be “Matter bridges,” Matter isn’t going to help with this use case. So it’s back to Homebridge we go.)
All solutions, including those under discussion in the following thread, require a separate dedicated server and some technical skill. The following statement is typical of the discussion:
Homebridge is an OSS Node.js server that emulates the iOS HomeKit API.
So be prepared for a pretty technical conversation.