So, my current whole house audio is powered by Chromecast Audios. Unfortunately they no longer make them. But you can still get them new off eBay. I know because I just bought 5 more (unopened from Japan) as part of finishing our basement

Mine feed two 12 channel (six room) amplifiers. I’ve got a mini in each room whose default speaker is the associated CCA and it works great. I have speaker groups so I can ask “hey Google, play music in the basement” and all rooms play.

Previously I used casatunes. They don’t do this anymore, but I bought a PCI card from them (it was a sound blaster hardware) but it was a 6 channel sound card and associated software that ran on windows IIS. It allowed both hardware and software streaming. I liked it but it never supported Google music and eventually I switched to the CCAs

I switched over to Actual last month, and am not looking back. I will miss the native android app, but it is an otherwise direct replacement. I was using YNAB4, and had forever.