My kids are grown now so my comment probably isn’t all that relevant anymore, but I don’t think there should be a set age to give your kid a smart phone. Different kids mature and learn at different ages, even ones from the same household.

For my kids, I got them their first phones in their early teens but those phones were somewhat restricted so that we could still communicate easily but we knew they couldn’t get into too much trouble with them. As time progressed the restrictions slowly lifted as we knew we could trust them more to not get into trouble with them.

I’ve always believed it’s not a parents duty to protect their child from the world as much as it is to prepare them for it. Of course kids are going to make stupid decisions if you let them go too far (we all have) so I think it’s more about slowly easing them into things and helping them make the right decisions the best we can.