How to add Alexa devices which are not supported with each App

I tried to add the Amazon device: alexa smart air quality monitor to the Ewelink app, but I can’t add it to Ewelink. How can I solve it?

Ewelink was relevant to the original poster because he was trying to operate a Sonoff device. You don’t need it.

You can - I assume - add the quality monitor to an Amazon device (Echo, Dot, etc)? You then need to add the Amazon Alexa app to Homey.

You can then try to add the sensor to Homey via the Amazon Alexa app.