libidn got retired in CentOS Stream 9 (RHEL 9) https://gitlab.com/redhat/centos-stream/rpms/libidn However there are packages depending on it in EPEL libgsasl #2038095 (exim #2037591). Would you be interested to branch it as part of EPEL 9 - otherwise I could help co-maintain it. This should be possible since libidn won't be part of RHEL 9 anymore.
Please feel free to request the branch and maintain it. You should have the access now. Thanks.
Thank you I did: https://pagure.io/releng/fedora-scm-requests/issue/42225 It seems that you can't simply replace libidn with libidn2 (at least in the gsasl case), since libidn2 does not implement all functionality that was part of libidn, since gsasl is explicitely looking for stringprep and this is not part of libidn2 https://gitlab.com/libidn/libidn2/-/blob/master/doc/libidn2.texi#L400-409
FEDORA-EPEL-2022-b2433fb973 has been submitted as an update to Fedora EPEL 9. https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2022-b2433fb973
Lost traction to push it - just did it. Sorry for the delay
FEDORA-EPEL-2022-b2433fb973 has been pushed to the Fedora EPEL 9 stable repository. If problem still persists, please make note of it in this bug report.