Tasmota

https://github.com/arendst/Sonoff-Tasmota

Web interface

SwitchMode

https://github.com/arendst/Sonoff-Tasmota/wiki/Commands#command-overview https://github.com/arendst/Sonoff-Tasmota/wiki/Buttons-and-Switches#switchmode

For 2-way wall switch,

SwitchMode1 1

or

SwitchMode1 2