The simplest idea is to put your phone with the luggage that you hand over for loading on the plane, and go through customs control with a second phone, making it look like it's the main one.
maybe the simplest idea is just to try and hide your installed apps or at least the ones you don't want them seeing.
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i haven't tested it out. to see how well it really works.
I have recently been through this procedure myself and customs officers check not only apps but also browsers and messengers. Also customs officers have special software that can access all the data in the phone memory.
I don't know how such checks take place in other countries, but in Russia we will not be asked to unlock the phone first. The customs officers will first take your passport from you and ask you to wait in a special area, and they will observe your behaviour.
More fun and positivity, customs officers have a lot of work to do and if you don't give in to provocations, they lose interest in you quickly.