@GrapheneOS The police will try to force you to do so, but this lawyer says that you are not obliged to. In fact, the right approach is to remain silent and then call a lawyer, and the police will probably try to dissuade you from doing so by putting a lot of pressure on you.
Christophe Boutry is a ex DGSI agent and a user/defender of GOS.
https://www.youtube.com/watch?v=aA4uCef4sFo
The problem is that some people in the comments claim that the police can force you to give them your PIN/passwords, but I would trust a lawyer more than random on the internet.
As a French citizen, it's not very clear.