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How Do I Prepare My Phone for a Protest?
(themarkup.org)
This is a most excellent place for technology news and articles.
You should probably leave your own phone at home when you do. You don’t want the burner phone and your own showing up on the same towers at the same time. Turn the burner completely off when near home or your personal phone.
That's good advice as well, but really only important if you're a long-term PoI. If you're just arrested for rioting/protesting, it's probably not essential.