I don’t recommend attempting this. Yes, it’s possible to lash up some adapters and route TV audio to CONNECT:AMP, but you will end up with unresolvable lip sync issues. With additional lash-up’s you could use the TV remote for Volume control, but this would be an ugly DIY project.

One challenge, no matter how you get the signal in to the CONNECT:AMP that you’re going to deal with is the delay inherent with the analog input, which is going to make lipsync somewhat of a challenge. Since the audio line in is looking for a line level input, you’re not going to be able to use your TV’s remote to change the volume, there is no way to effectively change the line in level, and the CONNECT:AMP, not being designed for this type of use, has no IR input. The CONNECT:AMP is also stereo only, and cannot handle any ‘Home Theater’ formats. It can be used to power surround speaker by a kludge , but it can’t interpret front and rear signals of any type. 

if you felt you might not care about these issues, I’d likely get some sort of HDMI switch that has an RCA line level audio output (if such a thing is available, I’d look on Amazon to see), and connect that switch in between my input and the TV, to extract the audio so I could feed it to the Sonos CONNECT:AMP.

All that being said, IMHO this entire setup is rife with oddities, and challenges, and absolutely not something I would want to attempt. And, I suspect, it would not be supported use by Sonos, so any time you called in to Sonos Support directly, they’d not be able to help. 
 

Edit: @buzz types faster, and is more concise than I am.

Ok. Thank you.