Issues with building RPM’s. There’s no specification for what an RPM is (unlike say deb).

Well the specification is “whatever rpmbuild version x.y.z does” and whatever other tangential packages happen to be installed on the build system.

Try building an RPM for CentOS 6 on a RockyLinux 8 system, or building for both of those on Fedora.

You can do it, but it’s real ball ache, and you have to jump through a lot of hoops.

Compare to building a deb for any version of Debian/Ubuntu on Fedora/RHEL it’s a doddle and predictable.