Hello,
It seems that if you program an E5 with your code, it’s impossible to put back the factory version.
Is it true ?
I would like to adapt the original source code to add some feature but the source code doesn’t seems to be public. Am I right ?
Thanks
Yep you are right, once you overwrite the default firmware you can’t reinstall back ! The original firmware (based on AT commands) can’t be modified as it’s closed source 
It’s probably based on the example of ST : github STMicroelectronics/STM32CubeWL/tree/de65a6e5e3aa178705e20c71f7d78db198a80ccc/Projects/NUCLEO-WL55JC/Applications/LoRaWAN/LoRaWAN_AT_Slave with a modified BSP to fit the seeed e5-mini design.
I found also a repo about Arduino on Lora E5 : LoRa-E5-mini - RevSpace but in progress.
Has anyone tried to ask for a compiled binary of the factory AT firmware?
I have no interest in modifying the source just would like to convert my mini boards to how they were when shipped.