How is a third party service, especially a self-hosted one, expected to meet those requirements? They seem to be lengthy, onerous, and also require a detailed vetting by the pypi team that is unlikely to scale beyond a few large hosting providers.
(What's more, this does relatively little to actually signal trust to someone downloading them. All it does is provide a signature that one of the big providers has built the package from a given source (but nothing about the trustworthiness of that source). This is a problem much better solved by reproducable builds and distributed verification of those builds)
Codeberg: https://codeberg.org/mfenniak/oidc-jwt Tangled: https://tangled.org/docs/spindles/workflows/#audience
I think OIDC tokens from workflows is basically table stakes at this point, since the alternative is a static secret, which is basically guaranteed to leak eventually.
All that's left is for PyPI to accept these tokens in their set of trusted publishers.
(I haven't looked at Tangled at all. If Tangled has a secret management story for its PKI that's stronger than a private key on disk and can demonstrate that a non-trivial number of PyPI users would benefit from federation, then it's a strong candidate.)
PKI definitely is still hard, but if it can be done well by a smallish number of trusted parties to the benefit of their users, this can have huge ecosystem benefits. Let's hope we live in that timeline.