I was turned back at the US border after a 12-hour interrogation

> Buy a burner phone. Populate it with enough information that it does not seem suspicious.

I'm glad this is something people actually started mentioning. It's hard to tell how bad a clean burner phone looks like. But I bet it could get you in trouble if you're already known by name for some reason (relative to a plain boring phone anyway).

This echoes earlier comments re “no privacy online”. Safest to assume that everything one does on line is public and has fallen into the wrong hands.