Hey GP.

Is what I suggest possible? It's quite hard to figure out now that the Chromecast Audio has been discontinued.

Chromecast 2 (cheap on 1-day, plus I have a voucher to use). I would buy an Ultra if I had to.
Google Home mini + hub

Plug CC into my AVR (Onkyo TX-NR747) HDMI port and leave that HDMI port active.
Set up CC as a "speaker" on Google Home, and request "hey Google, play Youtube Music on my speaker".

My goal is simply to be able to get Google Home to play music on my AVR. I figured a CC was the cheapest/easiest way.