Hi Spock,
We use the RASPBIAN STRETCH WITH DESKTOP 2018.4.18 image for the testing. it works well. please download it from https://www.raspberrypi.org/downloads/raspbian/. Please try and let us know if any issue.
Please follow <LINK_TEXT text=“https://developers.google.com/assistant … ev-project”>https://developers.google.com/assistant/sdk/prototype/getting-started-pi-python/config-dev-project-and-account#config-dev-project</LINK_TEXT> and click 
thanks
Seeed techsupport team
Bill