with the demise of the groovy Homekit integration approaching, I wanted to start a thread on alternatives that users might find.
Here is one. The developer has been making recent updates on their connector between ST, Homebridge and HomeKit that uses the ST API. This does require you to set up a Personal Access Token.
It misses a few features (in my opinion) but you can always contact the Developer and see if they can add them.
If you find other products, please post.
We should note that for those who are new to Homebridge, it is software that emulates a Philips Hue bridge, allowing it to be seen by a number of home automation platforms, including Apple HomeKit.
You will have to have an always on server device running Homebridge before you can use this plug-in.
And, yes, it would be easier if the SmartThings hub were a “matter bridge”—then you could just add it to the Apple home app without needing anything else. But SmartThings is only going to support Matter in a one-way in configuration. (Matter “controller,” NOT a Matter “bridge.”) You will be able to add most Matter logo devices to the SmartThings app, but not add the SmartThings hub and its devices to other companies’ apps.
I only mention all this because I expect there to be a lot of confusion over this in the next few months.
To bring SmartThings-controlled devices into HomeKit, you’ll need to use homebridge or some similar thirdparty solution. Matter alone won’t be enough.
Carry on. 
How reliable is to connect HomeAssistant to Smarthings and then access HomeAssistant through Homekit?
I do have 20 devices that only integrate with Smarthings and not with HA. If not - would have migrated all. Additionally - I am still not sure about stability of HomeAssistant over time.