An Apple TV used to treat many AirPlay speaker selections as temporary. tvOS 26 made it possible to remember a compatible AirPlay speaker as an output, which is potentially useful in a multiroom audio setup.
The practical test is whether a specific Sonos room stays selected after sleep and wake. Lip sync, surround formats and volume behavior still matter, so this is not a guaranteed replacement for a wired theater path.
Action: test one noncritical Apple TV and one Sonos room before changing the main setup.
