Yes, but the method varies depending on which brand/model of lights.
Philips Hue (through their bridge) and Lutron Caseta are both HomeKit-compatible. So they have their own integration with Siri which works very well, in some ways better than Alexa. (I have and use both.) And both have official SmartThings integrations.
Anything which is controlled by SmartThings but is not HomeKit-compatible, such as a zwave light switch or Cree bulbs can still be operated from an Apple Watch, but you have to do it by sending a voice text to IFTTT. So “Hey, Siri, tell house #turn_kitchen_ceiling_on.” This was how I used to do voice control with SmartThings before I got an Echo. It works, but it’s clunky.
I myself am quadriparetic, use a wheelchair with limited hand control. So voice control is essential for me. And I do use an Apple Watch, although I prefer the voice recognition on Alexa. So I use Echo for choice, but also use the Apple Watch daily. I now only choose Devices which work with HomeKit and Alexa, but fortunately there are good choices in lights.
But you can still use the IFTTT method with any SmartThings-controlled device, it’s just not as smooth as HomeKit. ![]()