> "Just leave your phone at home?" basically did not compute.

I wouldn't leave my phone at home either; a smartphone is the single most useful thing to have on your person when facing unexpected problems of almost any kind. And no idea about those particular protests, but protesters over here have started heavily coordinating and sharing information via phones, so you might have an actual information deficit without one.

That said, switching off cellular (or the device itself), disabling biometric auth, that might be a good idea.