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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.
Leave it at home.
I can understand the wish to film things; I recommend buying a cheap camera, maybe one to strap on your forehead (starting at $20) or an old compact digital camera. Something without any sort of connectivity. Something you can leave behind if the going gets rough.
They make much more practical chest straps for things like GoPros - you can sort of forget it's there and just let it capture everything. I did that while white-water rafting and it worked very well.
Also multiple SD cards, swapping out frequently so even if they grash the camera you still have something.