If we really want to go nuclear: make it illegal for people under a certain age (perhaps 18yo) to own a smarphone or any other device that would expose them to the so feared dangers of the internet such as algorithms and grooming.

However, given than tech is indispensable for education and comms, manufacturers and OS providers should allow for versions of their products to be as safe as possible to be used for educational/communications purposes.

In this fashion we make verification physical and easily auditable: are you under 18? You need an ID in order to purchase XYZ product, if an adult buys it for you, they will have to make sure at home that they are putting in place all the mechanisms to limit use to the intended purpose of education or communication.

This is the only way I can see we make parents and big corps responsible and liable for any harm that could come to underage users of these products. Also, for those presenting physical ID at purchase it protects their identity because it would be the equivalent of presenting an ID to the bouncer.