No, the Sonos Port will not work for TV surround audio - it provides stereo only audio and there would be a delay to any speakers of 75ms (minimum) and so the audio will be out of sync with the video on your TV screen.

To get 5.1 surround sound, you would need to cable 4 speakers and a powered sub, to two separate Sonos Amps and have one Amp wired to the TV using HDMI-ARC, or an Optical connection. One Amp (primary) will play the front HT channels and the .LFE channel …and the other Amp (secondary) will play the rear left/right audio channels.

You may find the following links helpful, that’s if you are looking to use Sonos for HT (and music) audio…

• https://support.sonos.com/en-us/article/set-up-your-sonos-amp
• https://support.sonos.com/en-us/article/use-a-third-party-subwoofer-with-amp-or-connect-amp
• https://support.sonos.com/en-us/article/set-up-connect-amp-as-surround-speakers
• https://www.sonos.com/en-us/blog/the-ultimate-guide-to-a-sonos-home-theater
   

Thanks for the reply. 
 

since Port has a digital out, if I have a 5.1 receiver with a digital input would Port work in that setup? 
 

my goal is to use components that I already have where possible. I’ll review the links you sent also. 

The line-in audio (stereo only input) will be buffered - that’s where the 75ms delay would occur, if that’s what you’re asking? …and the S/PDIF coax digital output will also be stereo too - so not HT 5.1 surround sound.

The ‘Port’ will be okay as a stereo music source to your Amp/Speakers - but I think you will encounter issues with TV audio/video sync and the ‘Port’ certainly will not play 5.1 surround sound audio, if that’s what you were hoping for.