I think the reason for this failure is the current unfortunate situation where Hatchling writes 2.4 metadata and Twine doesn't support it, yet. See also https://discuss.python.org/t/pep-639-round-3-improving-license-clarity-with-better-package-metadata/53020/151

I honestly hoped this would resolve itself faster, but since there wasn't a Twine release yet, I guess the correct fix is to pin Hatchling to <1.27.0 to get CI green again.

Thanks for tracking that down @hynek .