Are there any examples for WL55J to create a "native"LoRa device <-> device communication without using the LoRaWAN stack ?

Hello,

You can find examples in the STM32CUBE MCU package for STM32WL series (you can find it on the ST website).

In this package you will find in "Projects\NUCLEO-WL55JC\Applications\SubGHz_Phy" different applications that only use LoRa without the LoRaWAN stack.

Hope it helps

Regards