CentOS Stream (with and without EPEL)
Almalinux (with and without EPEL)
OpenSUSE or others. This is made for Fedora developers but I have no problem adding builtin configurations for other distributions as long as they're open source, have no legal problems that would preclude Fedora inclusion, and not behind a (psuedo) paywall. As an example, UBI doesn't meet this last criteria.
I will create a patch to add CentOS Stream so others can use it as an example.
Maxwell G referenced this ticket in commit 86f9106.
In addition to CentOS Stream 9+, release configurations for Almalinux, Amazon Linux, and CentOS Stream 8 (legacy mirror system) have been added.
I've implemented a fair amount of repo configurations. Folks are always welcome to contribute new ones, but I consider this completed for now.