A:Answer Normal patching is: Source Output/HDMI. >NOT to the ARC input of TV, often port 1. That's a dedicated port for passing audio on to the SONOS. --Your TV maintains onboard control of its audio output, either A-or-B, but not both.
Importantly, the do make HDMI splitters with multiple outs, for system integrators, enabling your AV receiver to receive a parallel signal to that going to the TV and on to the SONOS. See: Key Digital-brand.