I think the problem with this debate in general is that people aren’t recognizing the harm, and are clinging on to old ideas about how the world should work, ideas that just don’t acknowledge the reality of how things change as technology changes, or even just spreads. Rejecting the idea that there are harms, and thus nothing should be done, just ensures you don’t have a seat at the table at all when it comes to the inevitable decision to do the regulation.
However, the other harm is the recent IDScan hack which leaked 153M people's IDs. And regulation is not a solution here, we don't know how to implement a regulatory regime that will prevent these sorts of privacy disasters. Even if IDScan gets fines which kill the company (and I suspect they will not) it's not enough of a deterrent because no one will pay enough to actually provide proper security here.
Meta, Google, Anthropic, OpenAI etc can afford to pay for and deal with licensing. They also created these issues and would very much prefer not to have to mitigate the harm they do to adults (i.e. people with money to spend). Furthermore, it'd be great if they didn't have to worry about small time competitors emerging and growing too fast. Licensing under the guise of "think of the children" is perfect for them.
Meanwhile, the age flag in the operating system will be used for other forms of authoritarian control. It will have actually accomplished nothing other than limiting peoples' fundamental civil liberties.
Leaving it all completely deregulated and/or letting platforms implement it themselves to varying levels of success and personal invasion feels like the worst option to me.
"an RFC that gives parents the ability to communicate their underage child is using the device without revealing or verifying any further information." is no different to "turn on age lock?" that you see on website now. It requires the parent to be present, engaged and 1 step ahead of their kids, and if we could depend on that, then we wouldn't even be having this discussion.
For all the protections that the ISP cannot reasonably provide, one can consider creating a nation-wide (or EU-wide, or US-wide) official label, that device makers can obtain if they meet certain requirements. Parents can them make their choice. We have that for food etc., so why not for internet access mobile devices. Because from my perspective, the main problem that needs to be solved is that parents cannot monitor 24/7 what their children do on their phones.
Yet another solution is to create a top level domain for kids, restrict kid devices to that domain, and allow sites enter this domain only if they meet defined criteria.
Oh, and prevent ISPs and phone makers to sell 'for kids" products at a higher price. People can whine all they want about free market, but it's to protect our children.
Besides, I read about what happened with Spain and football, and from my understanding the issue was that they blocked not DNS but IP addresses. And problem domain is also vastly different, a priori: in that case, they faced sites that were actively trying to avoid blocking, while in our case, I doubt pron sites and such will try to do the same, because children are not their target audience.
An alternative could be to create a top level domain (TLD) "for kids" and restrict kid phones to it. Then in your TLD you can admit sites that meet minimum criteria (no pron, no terrorism, content and chat moderation for SNS).