I see the EU is inviting tenders for how to create their age verification to access sites (the big 3 porn ones) thing work.
Have to be honest, I don't think it will work.
Also, porn and the internet being what they are, I'm not sure driving curious kids to the smaller sites is actually a good idea.
https://digital-strategy.ec.europa.eu/en/funding/call-tenders-development-consultancy-and-support-age-verification-solution