I have now installed two of these, which use the residual current across the live wire power the circuit board without a neutral. Cost me about £14 each.

I’m using the eWelink bridge in to HomeAssistant right now but as soon as a Tasmota flash becomes a possibility I’ll be flashing them with that.

https://www.itead.cc/smart-home/sonoff-t4eu1c-wi-fi-smart-single-wire-wall-switch.html