At least on Android they've removed the ability to encrypt data stored on external media, so in exchange for the ability to do this you're carrying around everything unencrypted (except what individual apps might encrypt themselves).

I thought the play was to travel with a burner and mail the real phone to a drop somewhere in the destination country. Supposing you could just put all your sensitive data on a microsim or microsd and do the same thing, but this all feels like different colored wrappers on the same piece of candy: don't bring data you want to keep secret to the place where they're allowed to use force to steal secret data. Obv packages are subject to search and seizure at borders the same way you and your phone are but a package in the mail has the advantage of volume and relative anonymity. There are a lot of packages and not enough resources to seize and search all of them, and it's harder to tie the package to a person or entity that warrants increased suspicion if it's mailed anonymously from another country than it is to tie a phone to the guy whose pocket it was in when he tried to cross the border.

That isn't something that actually exists

But if the data is backed up on iCloud, Apple will provide it with a warrant.

Can be set to less attempts via MDM profiles.

Same for Android.

“just do not go to / via the US” is not a serious solution for a lot of people.

I think almost all countries do this if your name is on a list (as this person's is). It's the nature of the lists and what gets your name added to them that varies from country to country.

I've been to China recently. No phone search whatsoever. Their Internet is behind the famous Great Firewall though, but there is no issue using a (foreigner-only) unlocked sim or e-sim to access the rest of the Internet.

I travelled to the US three times and once had my devices checked. Travelled to China more than 50 times, never had anything checked.

UK passed a law for this recently. Germany has been doing it for a while.