There are two (or well, almost three) ways to do this today. All of them utilizes MQTT (MQTT Client and MQTT Hub apps).
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You don’t need additional hardware but need to subscribe to the service gBridge.
Guide to Connecting gBridge to Homey for Google Assistant -
You need to run Home Assistant or openHAB on a secondary device (RPi/Synology NAS/computer) and then configure your own broker and connect Homey to it and HA / openHAB to it and set them up correctly. Then you can connect either HA or openHAB to Google Home.
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This is being worked on by Athom (code/app awaiting approval from google as far as we know) and will probably work natively in the near future. But it could take time also, we just don’t know at the moment.
