Can I control a device connected to a SmartThings Hub with Alexa If that device is compatible with SmartThings but not compatible with Alexa? From what I have read the answer is No. I am confused by this as I thought the SmartThings Hub is compatible with Alexa meaning Alexa controls the hub and the hub controls the device regardless if the device is voice assistant compatible.
Any feedback around this would be much appreciated.
Thanks,
Depends on the device. If it’s a switch/dimmer, thermostat, bulb, lock, contact sensor or motion sensor, then yes.
Thanks for the feedback. Could you give me an example of when Alexa would not work. I am trying to understand why some devices couldn’t be controlled by Alexa since the hub is doing the work and the hub is controlled by Alexa.
Thanks again,
Alexa doesn’t “control” the hub. It just passes over a request.
As @Automated_House said, there are some classes of devices which can be connected to your SmartThings account where the echo/SmartThings integration will give you control of many different features, such as dimming or changing the setting for a thermostat, etc. That gives you the most natural kind of voice control and doesn’t require setting up anything special.
Separately, you can also use a “virtual switch“ to trigger a scene or custom automation (or routine in the classic app) which lets you do many more things. But it’s more work to set up and the voice Integration is not as natural.
Just as one example, you could use echo to change the location.mode by using the virtual switch method. 
Alexa only supports a limited set of capabilities that SmartThings supports. Some things that Alexa doesn’t support that SmartThings does:
humidity
blinds (unless they also have switch or dimmer capability)
rodent
accelerometer/vibration
siren
buttons
illuminance
etc etc