[novok]

IMO I think the better solution is to make a full feature smartphone an 18+ item, much like beer. If you are under 18 you only get a very limited 'call mom' phone with no video camera, chat limited to your family, maps to find your way home with and an otherwise very restricted set of apps. Police can take contraband phones from teens much like they can take contraband beer. They would have a distinct design so the types are identifiable.

No identity checking system needed for using the general internet as a result.

You can still have a family ipad, TV, xbox, switch, laptop, school chromebook, large clunky semi-pro digital camera for movie club, a separate dedicated audio recorder, etc but the key is to stop gossip networks with video recordings / snapchat and make the digital experience similar to what millenials grew up with, the last generation who didn't get a huge spike in anxiety and depression.

Yes many teens will still get around it, but the idea is to add a lot of friction so you stop the network effects that are causing this in the first place.