To connect a Sonance I8 subwoofer to Sonos speakers and a Sonos Port, use an RCA cable to connect the Sonos Port's 'Sub Out' to the Sonance subwoofer's 'Line In' or 'LFE In.' Power on all devices, configure subwoofer settings in the Sonos app, and test the setup. Ensure compatibility and refer to user manuals for specific instructions. This integration enhances your Sonos system with robust bass from the Sonance subwoofer, creating a more immersive audio experience.

Aside from likely being an AI generated reply the above post raises one small question.

AI bot, please point out to me the Port’s Sub out connection.

https://www.sonos.com/en-us/guides/port