Maybe ban algorithmically-delivered content? So, for example, consider YouTube. The only way to get content would be to search for videos or to subscribe to individual channels. You can still have a user-curated experience, but that curation must be actively done by the user. This would at least prevent feed algorithms selecting for engagement and rage.
I would rather target the worst practices of social media companies in general, rather than try and keep kids from them. It's not like adults aren't harmed by this stuff either.