There is a main issue tracker to report general issues. However, if you know you need to report an issue for a specific component, there is a list of below, too.
General Modularity issue tracker — For general issues or when it is not clear where to report specifically
MBS (Module Build Service) issue tracker — Issues regarding MBS upstream project specifically. If your issue or RFE changes the syntax or semantics of the MBS input or the MBS output (RPMs built in a module or resulting modular metadata), it does belong to General Modularity issue tracker. If your issue is related to particular module build in Fedora infrastructure, it belongs to Fedora Infrastructure issue tracker. Any other MBS issue can be filed in the MBS issue tracker.
libmodulemd issue tracker — Issues regarding the modulemd specification and the libmodulemd library.
DNF issue tracker — Issues regarding the "dnf module" command.