stfn, 
Hey #meshtastic people, don't know how many people are aware of recent braking changes, so sharing it:
Software version 2.3 changes the MQTT channel naming from msh/XXX/c to msh/XXX/e, so people using 2.3 cannot talk to people using 2.2 via MQTT.
Link to changelog: https://github.com/meshtastic/firmware/releases/tag/v2.3.2.63df972
