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Just to expand on @Stanley_4’s sound advice, what you describe used to work, as long as the device with the ethernet ports was connecting wirelessly to SonosNet (not WiFi). Whether it would still work these days, I’m not so sure, but I think so.
It does make far more sense to use a switch, as suggested - Sonos ethernet ports are 100Mb maximum, and Sonos systems generally do not take kindly to other devices using up their bandwidth (audio doesn’t take much bandwidth, but other uses can).