Chromecast Audio is dead and discontinued. Sonos is too expensive. The WiiM Mini is the true affordable streamer that does multiroom audio and more.
WiiM's Mini and Pro are the Chromecast Audio's real replacement
Reviews for WiiM Mini
WiiM Pro review: The Chromecast Audio Ultra we never got
WIIM WIIMMINI WIIM MINI WIRELESS AUDIO STREAMER
Finally, a HiFi alternative to Chromecast Audio: WiiM - RouteNote Blog
WiiM Pro AirPlay 2 Receiver, Chromecast Audio, WiFi
WiiM Pro AirPlay 2 Receiver, Chromecast Audio, WiFi Multiroom
WiiM Mini/Pro are perfect alternatives to Chromecast Audio
Finally, a HiFi alternative to Chromecast Audio: WiiM - RouteNote Blog
WiiM Pro AirPlay 2 Receiver, Chromecast Audio, WiFi