Here is a newb MQTT tutorial for 1.3

As of firmware 1.3.48. The inject message node in the prior test image will not work properly without modification. There is a change in what a valid JSON envelope will be accepted by the device for broadcast on the mesh. It looks like:
{
“sender”: “whatever you need here”,
“type”: “sendtext”,
“payload”: “whatever you want sent onto the mesh”
}
The “type”:“sendtext” is new.