Many might’ve seen the Australian ban of social media for <16 y.o with no idea of how to implement it. There have been mentions of “double blind age verification”, but I can’t find any information on it.
Out of curiosity, how would you implement this with privacy in mind if you really had to?
You can’t.
Age verification is not compatible with any remotely acceptable version of the internet. It’s an obscene privacy violation in all cases by definition.
Any implementation short of a webcam watching you while you use the site is less than trivial to bypass with someone else’s ID while opening numerous massive tracking/security holes for no reason.