Anubis Works

I like the idea but this should probably be something that is pulled down into the protocol level once the nature of the challenge gets sussed out. It'll ultimately be better for accessibility if the PoW challenge is closer to being part of TCP than implemented in JavaScript individually by each website.

There's Cloudflare PrivacyPass that became an IETF standard [0], but it's rather weird, and the reference implementation is a bug nest.

[0] https://datatracker.ietf.org/wg/privacypass/about/

Ship an arbitrary challenge as a SPIR-V or MLIR black box. Integrate the challenge-response exchange with HTTP. That should permit broad support and flexible hardware acceleration.

The "good enough" solution is the existing and widely used SHA( seed, nonce ). That could easily be integrated into a lower level of the stack if the tech giants wanted it.