Don’t forget signed attestations from “user probably has skin in the game” cloud providers like iCloud (already live in Safari and accepted by Cloudflare, iirc?) — not because they identify you but because abusive behavior will trigger attestation provider rate limiting and termination of services (which, in Apple’s case, includes potentially a console kill for the associated hardware). It’s not very popular to discuss at HN but I bet Anubis could add support for it regardless :)

https://datatracker.ietf.org/wg/privacypass/about/

https://www.w3.org/TR/vc-overview/