Robert Lie has created a series of 53 video tutorials on YouTube explaining LoRa & LoRaWAN. Most are short (<6 minutes) and well indexed, so you can quickly find topics of interest. Many illustrations and demonstrations of LoRa signals on SDR displays. Highly recommended. Complete playlist at

He also published documentation and slides at

Andreas Spiess also has a LoRa / LoRaWAN series of maker projects on YouTube at