It is funny to see all countries afraid of doing what should be done: fine and block the social media companies that don't fix their brainrot algorithms. Adults are not better at handling them than kids.
I have 3 kids, 2 use their phones like half an hour at a time, the other is completely hooked, hours and hours. If I don't intervene he doesn't dress in the morning, and continues until he really can't keep his eyes open anymore somewhere around 3am.
For him I use the parental control on my router. All his devices have time limited wifi, and he has no data in his phone plan. Since I've done this he goes outside more, and has developed other interests. Today he actually prepared lunch for us, a 14 year old boy!
My point is, I think it's better to help your kids use their phones moderately instead of completely blocking. I once heard from an alcoholic who always keeps beer in his fridge. Not to drink it, but to be sure you learn to deal with this shit, and wherever the beer is, you can manage not taking it if you don't want it.