The EU already wants to implement the zero-knowledge proofs for age verification
Its likely also one of the best solutions if i understood it correctly because the EU would only know that one recieved a bunch of certificates(?) (single use) but not where it got used and the website would not get any personal data

Zero-knowledge proofs are awsome, look them up
( ͡° ͜ʖ ͡°)=ε/̵͇̿̿/’̿’̿ ̿ ̿̿ ̿̿ ̿̿ (this is a threat but the weapon is not loaded)