I’m in a same situation as you are. Note that there’s nothing supported by SmartThings at this time!
There’s some discussion going on in this thread : Ceiling fan controller? , but I don’t think it fits well to the solution you and I wanted.
However, I’m thinking of a different approach. There’s this China product Broadlink that allows you to control Infrared and some RF’s. Those universal fan controls today are usually RF 433 / 315MHz.
I ordered this to hope that I’ll be able to integrate with ST :
I am going to pair with this:
Dimming wasn’t a priority for me, but I think this allows dimming. You have to double check.
More research to be done. Let me know if you come up with a better solution.