Universal Groups
Music Assistant has support for grouping playback devices.
Features
All devices (except Chromecast) can be grouped but not all will play in sync. See the individual players for their limitations.
Tip
Reminder Chromecast devices must be grouped in the Google Home app for perfect sync
Known Issues / Notes
UGP is on best-effort basis and might not work correctly with all player models or give unexpected results. For best results use standalone or syncgroup playback as explained here