Hi,
I´m trying to decide which dimmer to buy between the Fibaro Dimmer 2 and Aeotec Nano Dimmer.
Are both natively supported in the Smartthings app without using custom device handlers? Or do I have to use custom device handlers to get full functionality? Any known issues with respective dimmer?
Or do you have any other dimmers to recommend that works hassle free and are supported by Smartthings?
What country are you in? The device selection does vary considerably for dimmers. 
I live in Sweden.
I did also find the Qubino mini dimmer as an alternative (easy available in Sweden), seems to be natively supported in the ST app.