This is a bit smart-home specific... I've long wanted to build some smart speakers with Home Assistant's voice assistant and a multi-room music solution. Sadly I could never get Snapcast work to an acceptable level, but seems there is a new kid in the block now.

Sendspin (formerly Resonate) is an open synchronized music protocol. Currently being implemented within ESPHome. A few days ago they fixed some more memory issues and seems it's getting along. Maybe we'll get an open and working multi-room audio solution added to ESPHome soon.

I got it working on both an ESP32-S3 and an old ESP32 (with PSRAM). It's got nice features like the title, artist, album and cover art being transferred so we can just display that on a small TFT. And it's just about starting to work well enough. Now they need to finalize it, get some more things changed around in ESPHome and I can finally assemble some synced speakers for the kitchen and livingroom. Yay!

Seems it's early days for the server-side of it as well. We got support by Music Assistant. Other than that the (few) libraries warn they're still more or less just a tech demo. So as of now this is somewhat limited to tinkerers, but IMO looking really promising.

• https://esphome.io/
• https://www.music-assistant.io/
• https://www.sendspin-audio.com/
• https://github.com/esphome/esphome/pull/12284 (plus a bunch of related PRs)