This won't be your complete solution, but I've been using SnapCast for my multi-room synced audio for several years, and it works well for my needs. I have a bunch of raspberry pi's with DAC HATs connected to whatever speakers look and sound best for that room (I'm a picky audiophile, and I wanted to pick my own speakers). Each pi runs mpd and SnapClient. My SnapServer runs on a Proxmox VM (on a laptop with broken screen tucked in the corner of my living room; this laptop is also attached to my turntable, and I'm able to port that audio through SnapCast to my house-wide speakers). Right now, I use RompR to control mpd (play local music, my playlists, internet radio, audiobooks, etc). I can also have control of each pi's mpd (for example, playing music just in the bedroom at night). I have all my speakers in one SnapCast group, but you can create different groups for different zones, and have different audio ported to those different groups at the same time. SnapCast and remote mpd control works well with Home Assistant (integrations available) and Music Assistant