What?
ESP-now to MQTT to Home assisstant garage door opener button
How?
The software is mostly copy-paste from different examples, nothing special.
The hardware is a barebones ESP8266 module with a 3.3V regulator and a pushbutton that connects VCC from my ebikebatterys USB-port.
The ESP (sender) boots up and sends a short ESP-now message. A ESP devmodule (receiver) listens for ESP-now messages and forwards any received messages via serial to a second ESP devmodule (mqtt) that publishes the message via MQTT so Home assistant can react to it and open my garage door.
Ref links
https://randomnerdtutorials.com/esp-now-esp8266-nodemcu-arduino-ide/
https://randomnerdtutorials.com/esp8266-pinout-reference-gpios/