Fedora Linux has reclassified the CC0-1.0 license as allowed for content only due to concerns about patent-related language.

While the python-email-validator package can remain in Fedora Linux under a blanket exception for code files in Fedora packages prior to 2022-08-01, it would still be much better from Fedora’s perspective if the package could be offered under a different license. Some widely-accepted extremely-permissive licenses include 0BSD, MIT-0, and Unlicense.

I suspect there are other users out there for whom the CC0-1.0 license is becoming a problem.