In theory it is by possible by "blind attestations" by a 3rd party, in an indirect way, that is what you get by Cloudflare, where they monitor traffic from an "

In theory it is by possible by "blind attestations" by a 3rd party, in an indirect way, that is what you get by Cloudflare, where they monitor traffic from an "agent" using their own heuristics for identity, without sharing that identity with you.