This would require that SONOS build and test an App for each TV model. This is not very practical for SONOS,

Personally, I would not want to attempt using a TV remote and some sort of on screen display for playing music. Plus, the TV location is fixed. A phone/pad can follow me.

Do smart tvs not have a few basic operating systems, like Android or iOS?  I’m not looking to play music using my tv controller, I’m looking to play the tv sound through the Sonos system.

An obvious stumbling block would be network delay. Audio sent over the network from the TV would require a buffer at the receiving end to smooth out variations in packet transit times across the network. As it’s a real-time stream the receiving end can’t be allowed to run out of data, otherwise the audio will drop out.

It would basically be in the same situation as for Sonos Line-In, which needs a minimum buffer/delay of 75ms (often more). A delay of that order is sufficient to upset TV picture lip-sync.

Ok so that’s an excellent technical explanation even if I don’t understand it but is this something that is specific to the TV sound -- like it has to match the video?  Which is why it’s not a problem playing music from a phone?

If it’s just music from a phone then there’s no video picture, and a bit of delay doesn’t matter.

And if it’s an iThing playing video and sending audio over AirPlay it may be able to compensate for the delay by delaying the video to match. It does depend on circumstances though.

A music track could have been recorded decades ago. Delaying it another 75ms is not an issue. Delaying current TV audio 75ms will annoy many viewers.

Ok thank you both for your answers, that makes a lot more sense.  It never occurred to me that would be an issue.