If I use v2.3.0 of this repo with Arduino Core 2.3.0 for the ESP8266 my nodeMCU 1.0 (esp-12E) module is discovered by the Alexa app. If I update to the 3.0 version of this repo my device is never found nor is anything other than the wifi connection and free heap shown in the serial console.
In both cases I was using the provided example sketch and only changed my wifi creds and the plug name.
I did try adding
#define DEBUG_FAUXMO_VERBOSE true to the 3.0 version of the sketch but it didn't change a thing.