> A trick I’ve developed, when giving my contact info to new people, is to enter my phone number on their smartphone myself, and install Signal for them.
don't... do that. don't install stuff on anyone's phone unless they've told you to.
Even on ios it's technically not required. You only need touchid/faceid/password to add the app to your account. Afterwards you can freely install without additional authentication.
Depends how you have it configured on android at least, if the phone is unlocked already you can install from the play store w/o additional permissions unless it is a paid app
don't... do that. don't install stuff on anyone's phone unless they've told you to.