Verified and working on all Alexa 2nd generation units. Flashed onto a Sonoff S20. Voice command from alexa works great. On/Off button on S20 Sonoff plug also works great.
This works on esp8266 type devices.
NodeMCU chip device verified working.
"@estauseb I have a NodeMCU chip. I did the change you suggested and I am now able to control the chip with my Echo Plus."