Some community members have used an electric strike successfully:
There are also retrofit smart locks which fit over the existing deadbolt and just turn it. That’s probably the simplest solution. It’s not visible from outside the house, just inside.
Unfortunately, the only one that is compatible with smartthings is the Dana lock, and it doesn’t get great reviews. But if you get it from someplace with a good return policy, you could try and see how it works for you. Make sure you get the model that also has Z wave if you want to integrate with SmartThings.
The August lock is the same type and gets better reviews, but it isn’t compatible with SmartThings at the present time.
I’d be careful attaching anything that uses a magnet to the deadbolt itself as The turnbolt could itself become magnetized over time, which throws off the detection. That’s where you just have to be really careful about placement.