Have you tried recently? I’ve been playing with music-assistant, snapcast, and shairport-sync on some raspberry pi zeros. Synchronization has seemed to work incredibly well during my experiments.
Sonos syncs things up well-enough that a pair of them can be used in stereo. The stereo pair will play in-phase (allowing for imaging like with conventional stereo rigs), and stay locked together even as devices are added and removed to/from a group.
