Best answer by MikeV
No, there is no way to do this. The Play:1 doesn't have a line-in connection, and the Play:1 also doesn't support Airplay 2.
If you have a Sonos One (the voice-enabled speaker that looks similar to the Play:1), that speaker supports Airplay 2 and could be used to send the sound from videos you watch via Airplay to the Sonos speaker. Though I'll note that using Airplay from an iPhone or iPad to the Apple TV won't then have the sound sent to the Sonos speaker. One video stream cannot have two Airplay connections (i.e. iPhone -> Apple TV + Apple TV -> Sonos).