Never use a dimmer that controls the current load to a smart bulb, whether that dimmer is smart or not. Basically you need to allow a smart bulb to control its own current draw and you leave the current on the circuit on all the time. Otherwise, you will eventually burn out either the bulbs or the switch, and can start a fire. You’ll see a lot of people who said they have done it and it was fine, but that doesn’t mean it’s safe.
You can use a smart dimmer on a different circuit (or battery powered) and have the smart bulb “follow it” through wireless commands, and these work very well. There are battery powered Devolo and Popp switches in the UK that works very well with smart Bulbs and with SmartThings thanks to a custom device handler by a community member.
Or you can just use the Phillips hue battery powered dimmer switch which is available from Amazon.co.uk and is also very popular. It doesn’t have direct integration to SmartThings, but it works is a parallel means of control, and the status will get updated in smartthings the next time the bridge is polled, within five minutes. We use these at our house in the guestroom as an intuitive means of control.
https://www.amazon.co.uk/Philips-8718696506943-Personal-Lighting-Wireless/dp/B0148NMVX8
Both are good choices if you want a wall switch with smart bulbs. 
Or you can use a smart dimmer like the Fibaro with dumb dimmable bulbs, and that also works very well. You may have to experiment to find just the right brand and model of dimmable dumb LED to work with the Fibaro without flickering, but it should be doable.
Just don’t use any dimmer to control current flow to a smart bulb.