And that is why I have attempted to write some “How To” articles here.
And also why we contributors have started slowly but surely working on documentation for the distro on the user side but we also need to write documentation for the contributors particularly at this time for Developer Group and QA Team.
These links might help with the issue in this thread.
https://wiki.openmandriva.org/en/OpenMandriva_Release_Plan_and_Repositories
How To edit repos for dnf in your OM Lx system
After reading those two then this one should make sense and work for you.
How To quickly enable/disable repos in Cooker (Applies to other versions if you edit the commands accordingly.)
I hope this helps. People can save themselves a lot of headache if they do a little reading before they start package management with a new system or new approach as we are.