Pleased I picked up a couple of backup chromecast audios while you could still get them (as well as half a dozen of the Amazon Echo Input equivalent when they were $10 each), but this looks like a good option if that all goes to pot.
Obviously Amazon and Google's sales disagreed, but I would have thought there were enough people who wanted to enable streaming on their already good audio systems not to have discontinued the audio-output-only devices, and I had then hoped that Google would at least put an output jack on their later Home iterations.
I set my system up at the end of 2015 when the chromecast audios were released, and the seamless multi-room audio and interactivity I get from my multiple chromecast-connected "dumb" amplifiers and speakers throughout the house is something that I'm still impressed with even after all these years.