So I recently upgraded to a Mac Mini M1 with Big Sur and have been using a Sonos One speaker connected via AirPlay. 

I’ve been reading about many variations of audio syncing issues on various forums, and thought I would share my specific issue & what I’ve found to be an actual working solution. My issue was that after my Mac went to sleep (either after me putting in sleep mode or walking away from the computer for a time) it would begin to get out of sync, particularly via Safari videos. The only way I could resolve the issue was a restart of the Mac.

Simply enough I disabled sleep mode & sync issues magically disappeared for me... although it sucks as I would prefer to leave my Mac to go into sleep mode, but for the sake of keeping in sync this is the only way I can get it working for me.