I am still a very happy Squeezebox user. The product is officially dead from Logitech but the ecosystem is alive and well. This proves to me that it was the right choice to buy something backed by open source.

Around here you can still find used squeezebox hardware for a reasonable price. If you want fresh hardware then go for Raspberry Pi with a DAC hat.

If you want to get started easily today then look at https://www.picoreplayer.org/

If you run Windows then Squeezelite-X is a must-have: https://www.microsoft.com/en-us/p/squeezelite-x/

And if you think the interface looks old - then get the material skin (it is just a checkbox on the add-ons page in LMS) https://github.com/CDrummond/lms-material

The "Squeezer" remote works very well for Android. https://play.google.com/store/apps/details?id=uk.org.ngo.squ...

I may be misunderstanding your question but I'm a big fan of Denon (or Marantz) receivers w/ HEOS. Their AVR line can support up to 3 zones and can be paired together. I have 11.2 and 9.2 powering 18x speakers and a sub in my house. You can use a single receiver to play music outside by our pool and simultaneously play 5.1 over the living room for sports or movies. It also handles the connection to Spotify (et al) directly so I can take a call or leave the house with my phone and the music will continue to play.

I'm not too familiar with Sonos but I've been using this for years. https://en.m.wikipedia.org/wiki/Logitech_Media_Server All my players are now raspberrypi based. Works a treat.

If you're in the Apple ecosystem already, Shairport can provide multiroom audio if you don't already have an Airplay setup: https://github.com/mikebrady/shairport-sync

I don't know what "traditional stereo" means to you.

My music is stored on a computer sitting near a TV and a Yamaha receiver, which runs five main speakers and two subwoofers.

There's a powered speaker set hooked to a Chromecast audio in another room, and a cheap old laptop running an old Yamaha receiver with 2 mains and a sub in the living room.

forked-daapd (you'll want the current version out of github) runs on the main computer and has a web interface. It can talk to the Chromecast and the laptop and the main receiver to send the same audio to all of them. Delays can be adjusted.

I hardly ever do that. Instead, I call up music in whatever room I'm in.

Chromecast audio while it lasts, bubble upnp also works

Chromecast audio