Here is a link to the official Xiaomi website, which mentions that the Smartmi Model 1S with touch display can be controlled with Google and Amazon Alexa voice assistants:
Xiaomi Smartmi Model 1S with Touch Display (German website).
The product description states:
"With the Smartmi Home app or...
Have recently bought in Switzerland the Xiaomi Smartmi 1S Smart Heater. Everything has been set up so far without any problems. Also the linking of Xiaomi Home with Alexa has worked, only unfortunately this smart heater is not found in the devices in the Alexa app.
Am I doing something wrong or...