iPhone and Android both have features to help with this, but here are a couple of other things you could try. First, take a careful look at your notifications and think about exactly which apps you need second-by-second updates from. Most of them you probably could turn off, and it’s usually also possible to mute chatty but inessential group chats. Then check in on the stuff you care about when you want to, not when someone else wants you to. Second, take a look at the situations you’re in when you’re using your phone more than you want to. Are you trying to escape from something or avoid dealing with something? Try finding ways to address the underlying thing, because the phone is unlikely to be the only thing going on for you. And also, if you look at photos of people on trains from 50-100 years ago, almost everyone has a newspaper open. Fascination with rectangles that allow you to opt out of social interaction and learn stuff is not new, or necessarily a problem.