Putting a Sonoff in your wall switch box - #117 by Rhavin42 - Share your Projects! - Home Assistant Community
electrical - Can a Sonoff Basic Switch be connected between a wall switch and a light? - Home Improvement Stack Exchange
Wiring Diagram for SONOFF / ITEAD WIFI Light Switches in 4-Way(3 Switches controlling same lights) or 3-Way Hallway Installation with EWELINK App — Steemit