> How do you prevent kids using social media without 100% surveillance or not allowing internet access at all?

I don't give them a phone, and all the screens in my house are in the shared living space. They also don't know the WiFi password, should they try to sneak in a device.

Could they use a friend's phone? Sure. I'm not really concerned in that case, because there's honestly nothing I can do, but it's such minimal exposure with a huge barrier that I doubt it's effectiveness in sustaining much addiction.