No unsupervised access to any techno-gizmo until they're like 7 or 8, besides a dumb phone to call me or mom or watching me play/do things, maybe play together sometimes or limit it to formative things. Ain't no hypothetical child of mine gonna be raised by an iPad and cocomelon, and since I don't necessarily trust other parents to raise their kids decently I would get them a dog or 2 to play and bond with.

Then, once they start being old enough I will give them their own tower computer, obviously with Linux, privacy-redirects, limited access to the internet (I'm mostly gonna let them access games, wikipedia and stuff that is formative) and their access to YouTube is gonna be via FreeTube with channels I think they'd benefit from watching as already subscribed (plus whatever interest I know they have). Throughout the time I will be teaching them things, indulging their curiosity and gradually explain, reveal and open up things to them. Of course I'd also secretly monitor what they're doing, not to judge but to make sure they're safe, until I know they can safely navigate on their own. As for phones they're getting something locked down with some custom ROM like /e/OS or whatever and just the bare minimum they need to function (Signal to talk to me and mom, calendar, alarms, etc). No social media for them, they at most get to see some of it via privacy frontends. I want them to grow up in a way that the internet is a place they can leave.

Once they've teenagers and understand things I'd start gradually letting them do their own things and gradually giving them more access, allow them to make mistakes and be sure to be there for them to learn rather than just punish. The goal is that by 18, when they'll have full access, they're digitally literate and can safely navigate on their own, or at least be as careful as 18yos can be. At that point they'll also have to gradually start paying for their stuff on their own.