Actually…every SmartThings device is “RF.”
“RF” just means “radio frequency.” But there are many different frequencies and protocols in use. Zwave is RF. Zigbee is RF. Bluetooth is RF. Wi-Fi is RF. Ademco/Honeywell is RF.
None of these can talk to each other.
So you need to know the exact frequency and protocol being used by the RF device before you can figure out whether or not it can talk to SmartThings.
In this case, the OP mentions homelink. That is a standard garage door controller protocol used with many different cars.
There is a Z wave device made by Wayne dalton which can bridge home link to Z wave. Which sounds great, but unfortunately that specific device is a scene controller which will not work well with smartthings. There’s just no good way to program the scenes into it.
There are a couple of options, one of which is to use a vera as a secondary controller (it works just fine with the Wayne dalton device) and there is even a community member who completely hacked the Wayne dalton device and shifted it over to Zigbee. But that requires physically manipulating the device and adding a new radio.
My suggestion instead would be just to use a different device which can communicate well with SmartThings and ignore The existing home link buttons.
The Remotec 8 button device is about the size of a single gang light switch. It’s battery-operated and works well with SmartThings. Each button can be pressed, double pressed, or long-held so you get a total of 24 different codes from the one device. It should fit well on a car flap.
You can read about this device and other battery operated devices, including a couple of key fob options, that could work well in a car in the remotes and buttons FAQ:
But the Homelink frequency is not a frequency that SmartThings can receive, so if it were me, I just wouldn’t bother trying to use those.