Hi Pierre,
I am very tight with time to meet a deadline but would like to see if I can make some time for you.
First of all I am not using Linux, I use windows but my instructions wont be far from how it is done in Linux.
To start with, i tried to use the source code (I-CUBE-LRWAN) provided by STM without modification. There are 3 different examples of codes ATSLAVE, EndNode and PingPong. The first two can connect to the gateway but PingPong is for 2 end devices. Read these files for directionsExamples of AT commands on I-CUBE-LRWAN - Application note.pdf (631.9 KB)
I also got help from these links.B-L072Z-LRWAN1 Discovery kit · Microshare and https://www.hackster.io/victorffs/environmental-sensing-using-lora-and-stm32-c0136e
Try it and let’s continue. I hope it helps
Thanks