Finally, yesterday we received good news: The USB works despite the erratum.
So note for everyone that wants to use the USB on STM32L with ChibiOS, in your board.h set the USB pins in INPUT mode, not in alternate event if the USB is an alternate function.
Well lots of fears the day before yesterday, and lots of relieves yesterday. One last unknown point, will the SX1231 works? The PCB are almost soldered, I will set a test program, to get the version number of the SX1231 through SPI.
For the FRAM, I wrote a complete program test, with no surprises the FRAM read and write correctly on every addresses, and the sleep mode works fine.
I also had the description of the stateless synchronisation in the article “What is WaDeD” in the protocol section.