The maintainer of the Homebridge - SmartThings app (@tonesto7 ) has moved the app to Hubitat, and has archived the SmartThings version. The README makes it clear that the SmartThings app is no longer being maintained.
The GitHub repo for the Hubitat bridge is here.
I don’t have experience with this (yet - I’m hanging on until we know about the Groovy end-of-life plan), so I can’t answer the second half of your question, other than to observe that with The SmartThings - Homebridge app, the devices went from SmartThings to Homebridge and then on to Homekit and Siri, not the other way around.