A bit of good news, although this would be a very complicated solution…
The amazing @taustin has created an Edge option to enable SmartThings/MQTT integration for the new architecture. (The topic title is a clickable link.)
Why is that good news, you ask? Because there are several available MQTT plug ins for HomeKit, including some that run with HOOBS.
So…you could go SmartThings—>MQTT—>Homebridge.
Obviously clunky, inelegant, tedious, and requires yet another device…but maybe better than nothing for some people.
Clearly it would be better just to have a new ST plug in for Homebridge but I’ve not yet heard of anyone working on one.