FAQ: Confused by "Regular" Hub and "ADT" SmartThings Hub. Need clarification (2019)

The ADT panel itself is a hub, and only functions as a hub in SmartThings. It has to be the master on that location, and it does not work with any other smartthings hub. Like I said, unfortunately it’s just not going to work the way that you imagined. It’s not an add on to your existing system.

If you are just looking for a button for your current system, see the following FAQ:

FAQ: Full list of buttons and remotes confirmed to work with SmartThings [Not all devices listed work with the 2020 Platform]