Patches for league/csv don't get patched for drupal 9 (https://github.com/civicrm/civicrm-core/pull/24046)
It's not so much a regression as a recent change outputs warnings and doesn't work as intended, but effectively it's not doing anything different than before so it's not a functional bug yet.
After https://github.com/civicrm/civicrm-core/pull/24046
Applying patches for league/csv
https://raw.githubusercontent.com/civicrm/civicrm-core/cacdbfaeaed8e04d504bf2fc604536137c03abeb/tools/scripts/composer/leage_csv_fputcsv.patch (Adding in eol support to fputcsv for php8.1)
Could not apply patch! Skipping. The error was: Cannot apply patch https://raw.githubusercontent.com/civicrm/civicrm-core/cacdbfaeaed8e04d504bf2fc604536137c03abeb/tools/scripts/composer/leage_csv_fputcsv.patch
https://github.com/thephpleague/csv/commit/380f884922a6cdaaaaab3ad4bfc7d1d710af736e.patch (Remove deprecated flag from php8.1)
Could not apply patch! Skipping. The error was: Cannot apply patch https://github.com/thephpleague/csv/commit/380f884922a6cdaaaaab3ad4bfc7d1d710af736e.patch
https://github.com/thephpleague/csv/commit/613db0b20157a1114cb1f9a801bd4c9c1f609cdf.patch (Fix php8.1 deprecation errors part 1)
Could not apply patch! Skipping. The error was: Cannot apply patch https://github.com/thephpleague/csv/commit/613db0b20157a1114cb1f9a801bd4c9c1f609cdf.patch
https://github.com/thephpleague/csv/commit/49e2b08ca025ebaf87a904b5645f535c807b6f10.patch (Fix php8.1 deprecation errors part 2)
Could not apply patch! Skipping. The error was: Cannot apply patch https://github.com/thephpleague/csv/commit/49e2b08ca025ebaf87a904b5645f535c807b6f10.patch
https://github.com/thephpleague/csv/commit/b83e972caea3cd22e7aaf65c5cffff1d49b46b69.patch (Fix php8.1 notice issues part 3)
Could not apply patch! Skipping. The error was: Cannot apply patch https://github.com/thephpleague/csv/commit/b83e972caea3cd22e7aaf65c5cffff1d49b46b69.patch