If the nation state whose border you are crossing is part of your threat model then assume they will run a forensic examination of your phone, will deny you entry if you won't provide access, and will seize the device.
Use a travel phone that is factory reset before the trip and otherwise spends its time turned off. Also assume this phone is compromised and be full prepared to turn it over along with complete, forensic, access upon request.
Upon arrival in the nation, purchase an unlocked pixel and load GOS on it. Use a secure tunnel to download any data that you need on that phone from your server outside of the nation. When done with the trip either dispose of the phone or place it in secure storage until your next visit (safety deposit boxes and law offices are both generally good choices).
Basically, don't cross a national border with a device that you aren't willing yo unlock and have a full file system extraction performed on.