I got it! The sesame I have been waiting for almost 4 months: my main employer has validated my request for leave.
I can go on an adventure again. I am delighted!
The difficulty was not so much the duration of the leave, or its different types (some are even anticipations of vacation rights not yet acquired) but rather that it is almost impossible to know my activity in more than 6 months.
I still have to renew my passport, next week. But it should only be a formality, despite insane delays: nearly 6 months waiting to have an appointment at the city hall.