Just in case it helps anyone getting here given this topic's title: Arduino LoRaWAN sketches for the Ideetron Nexus board.
The Nexus board is not an ESP8266, but an Atmel ATMEGA328P with RFM95W or RFM98W. I've not used it, nor the above sketches.
@rvweert, what's your final setup with the ESP8266 and RFM95W?