Please branch and build libcrystalhd in epel9. If you do not wish to maintain libcrystalhd in epel9, or do not think you will be able to do this in a timely manner, the EPEL Packagers SIG would be happy to be a co-maintainer of the package; please add the epel-packagers-sig group through https://src.fedoraproject.org/rpms/libcrystalhd/addgroup and grant it commit access, or collaborator access on epel* branches.
Please don't build it for ffmpeg (in any case), this is an optional and deprecated library
I've dropped this as a dependency for ffmpeg in RHEL/EPEL.