I wouldn't allow them to have a phone at all until they're around 12 to 14 (just like my parents). When it comes to the internet on a computer, the same thing would apply, but they can when supervised. If possible, their only web browser on their internet device will have uBlock Origin installed with custom block lists to prevent them from accessing websites they aren't supposed to. I would also like software (whether I'd have to program it if it doesn't exist or not) to prevent them from using their devices at bedtime. Not a father, but those are the basics of what I'd imagine I do. Expect one last thing: Roblox is completely out of the question. I don't care how much they beg. It's a predator nightmare so it would be completely banned