Packages in the EPEL-8 repository are volunteered by Fedora packagers via requests by interested users. If a package you are looking for is not there, please look at https://bugzilla.redhat.com and see if a request has been opened for your package to be built in EPEL-8. If it hasn't please open a new ticket. Some packages may not be able to built in EPEL-8 due to missing deps which need to be added.

Ehm, maybe I was not clear.

I'm trying to build Remmina for EPEL 8 (I'm the maintainer of the package), but the avahi package is one of the "broken" ones where only the base package is included in RHEL, while the subpackages of it (avahi-devel, etc.) are missing, as per the link above. Also on the CentOS builder all packages are forbidden (403).

This is the same request as all the others here (libbluray, etc.).

Thanks.

CentOS builder with forbidden links: https://koji.mbox.centos.org/koji/buildinfo?buildID=112

We now have a formal policy to allow EPEL8 to build with these missing packages.
https://fedoraproject.org/wiki/EPEL/FAQ#RHEL_8.2B_has_binaries_in_the_release.2C_but_is_missing_some_corresponding_-devel_package.How_do_I_build_a_package_that_needs_that_missing-devel_package.3F

You need to open a CentOS issue[1] that states what devel package is missing and packages it is affecting. File the bug against the CentOS-8 Project, with the Category of _unreleased_devel_packages.

If you are unable to open a CentOS issue, please let me know, and I will open one for you.
If that is the case, please let me know specifically what package are missing, and what packages cannot be built because of it.

[1] - https://bugs.centos.org/%7CCentOS

Thanks, opening it there.

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/epel/steering/issues/99

Please continue any further discussion there.