I currently pay for qustodio. He can pown that thing in so many ways it isn’t funny. I have had multiple conversation with thier support, and usually the answer is that they can’t do anything about that because android doesn’t allow them to. For the pc it is windows of course, and they allow even less. Given the age of your kid now, there may not have been as many youtube videos back then explaining how to get around these parental controls. But there are now.
I have a technical background, so I can understand the things he is doing. Like I know what a vpn is, and how it can be used. So I can tell him that if he installs one there will be punishments. But most parents wouldn’t even know what it is, and if they got an alert about it, would probably believe whatever story thier kid told them about it.
And don’t get me started on the horrible parental controls on the switch. And roku effectively has none (they only work on the roku channel).
If a kid has any ambition, they can get around the vast majority of controls. And if the parent is not technical, they have no chance of really stopping a kid who wants to access something.