Sonos Airplay via Mac - poor sound quality

I recently bought a pair of Sonos Ones I have them set up as a stereo pair and if I play music through them using the Sonos Controller everything works beautifully. However, with the new AirPlay functionality I thought it would be great to use them as speakers for my Mac. My Mac OS is up to date and I can see the speakers in the sound menu and play sound through them. My previous set up was to use the speakers built into my monitor. Unfortunately the sound played through the Sonos Ones via Airplay is poor quality - I have tried playing things on YouTube and things on Spotify (not using Spotify connect) on the computer and the sound is rather "muddy" - it is much clearer when coming out of the monitor speakers.

Since then I have read that Mac OS only supports Airplay 2 via iTunes and not through the system audio. So I tried playing through the Sonos speakers via Airplay directly from iTunes rather than choosing the system sound output to the Sonos. And when I did this the playback was perfect.

I have tried a few 3rd party apps like AudioBridge, SonosAir and AirFoil but these end up with quite a bit of audio/video sync issues with YouTube (where as using the AirPlay option built into mac has no sync issues but sound quality issues).

So my questions really are:

- Is it true that Airplay 2 is not supported for system audio on Mac OS? And that it is just some backwards compatibility that is allowing it to play through the Sonos now but with issues?

- In the past when Sonos themselves didn't support Airplay there were apps like AudioBridge etc which allowed streaming to the Sonos speakers via AirPlay. Does anything exist to do this via AirPlay 2?

I realise Sonos isn't designed to be used for computer speakers but I'm just trying to solve the problem as it would be great to use this single speaker system for all my sound.