Sonoff”s tiny little Sonoff Mini Extreme (MINIR4M) R4 Matter version module is one of the smallest WiFi relay modules on the market, so it fits into even the smallest wall box.  It may be connected to eWeLink Cloud or to Sonoff iHost hub locally through WiFi, or connected to a Matter compatible local hub.  It has switch input for a wired wall switch, so it’s a perfect product to add smart control for a traditional wired switch.