Connect non-smart TV to sonos to play Youtube playlist from laptop

Anything that your TV is playing, no matter what the source, can be sent out of the connections on the back, either RCA if it has it, or preferably optical. Those can be plugged in to the Connect. Now, it will incur a delay of about 70ms, I'm told, so the sync with the screen of the TV might be problematic for you. If so, you should invest in a Playbar, which doesn't incur this same delay.

Sonos, for better or worse, has chosen to promote the Playbar as the device to connect to the TV, and tend not to respond to requests here regarding the Connect as a device to drive sound from a TV. But if you're willing to live with the delay (and in a party atmosphere, it might be significantly less noticeable, then that's the way I'd go).

Also, just in case, be aware that you'll only be getting stereo, the Connect is not set up to deal with a 5.1 signal.

I personally don't find the delay a problem with lip sync - Others may be more prone to seeing lip sync and disagree.

However, you will need to turn down your TV internal speakers as the delay will cause an echo (like stadium echo) with the sonos and TV speakers both on because the Sonos speaker will be ever so slightly behind the TV.