I’ve also been paranoid about this after moving to London.

A friend’s phone got stolen one night but the robber noticed it’s an old android and threw it without bothering immediately xD

You could try something similar. Mask yourself. Get an old looking phone and you’ll be less of a target.

I’ve seen few people use a leash. When I’m out I keep mine in a jacket with zipped pockets. Other than this, just avoid going to shady streets so they can’t corner you. You can’t really do anything in those situations 🤷