Smoking ban in bars and restaurants seem to work. So doing same with phones in schools during lesson time does not seem unreasonable.

I agree it is not unreasonable, but I'd also note that bars have their livelihood at stake. While a child has their phone at stake, you cannot threaten their livelihood without a trip to prison.

There are no material stakes to the child other than losing their entertainment device. Might as well break the rules.

This and taxes, it's much much harder to get cigarettes as a teenager now because of the price

Limited restrictions for specific times and places is totally reasonable, I read the parent comment in a larger scope as it was about stopping addiction.

If you would like to prohibit e.g. gambling mechanisms in games or social media you need a legal framework and then you investigate and fine the firms that don't adhere to the rules. This works very well in the EU as seen by the example of apple and facebook last week. It's not perfect but what is?

The EU still largely allows for lucrative gambling mechanisms, they just can't be predatory or deceptive. Which I agree is probably the best approach, coupled with advertisement restrictions etc.