For Amazon Alexa, you have to install the Homey Skills. Then, you have to invoke it by calling: “Alexa, ask Homey to turn on the lights”. You can’t just say Alexa, turn on the lights.
For Google Assistant, this is the part where it gets very confusing. It supports Google Assistant as in the app and not Google Home. I made the mistake of trying to find out how do I install the Homey App on my Google Home.
You are supposed to link Google Assistant with your Homey and only Android phones can do that. Visiting the Homey Google Assistant link on iOS devices does nothing.
Also, your Android phone needs to be in English (US) locale. You can change it in your phone settings. Other locales will not work as I have tested it with English (Singapore).
Once you have linked up Homey with Google Assistant, that is when you can use your Google Home to invoke Homey. Similar to Amazon Alexa, you need to invoke it by calling: “OK Google, ask Homey to turn on the lights.”
Unfortunately, that is not the case for me. After linking up, I could not get it to work. As you can see from the screenshot below, I encountered an unknown error.