The HACKING and README-hacking files contain advice to send patches to the email address in the respective program's --help output.
However, --help output might not contain any email addresses, such as for example in the coreutils that ships with Ubuntu 25.04. Looks as if both PACKAGE_PACKAGER and PACKAGE_PACKAGER_BUG_REPORTS need to be set in order to have at least one address there. Maybe some rephrasing of the hacking docs or adding fallback info there in case of no other email address source would be in order. Ville
