Just recently, I was able to successfully get my add-on for the text-based Google Assistant working on Hass.io.
Here is the add-on repo:
Once installed, the setup is similar to https://home-assistant.io/addons/google_assistant/
So, it needs the google_assistant.json file added to /share
Also, it follows the same OAuth setup.
Once completely running and set up, you can broadcast a text message to your Google Home devices using:
http://hassio.local:5000/broadcast_message?message=[YOUR TEXT MESSAGE]
This will enable you to broadcast a text message to all Google Home devices without interrupting your music that is currently playing.
It is extremely useful for when you want an alert to play based on some automation, but you don’t want to interrupt and stop the current music or anything.
Feel free to let me know any comments/suggestions.