It's a massive swing and a miss that GrapheneOS has a religious opposition to a VeraCrypt-style hidden volume arrangement that allows different passwords to unlock different OS volumes.
It would be vastly superior to their current solution, which basically guarantees contempt charges.
I hope they change their mind soon!
This. There should be a password that unlocks to a fairly minimal, but not too minimal configuration that wouldn't have anything of interest on it.
The problem is it will be detectable and detected and then the password demanded and a failure to provide it will result in charges. I think unfortunately the answer is the phone has to be plausibly empty when crossing the US border, they should focus their efforts on being able to store the full state of the phone remotely and encrypted and being able to restore it easily.