Backup Package Registry

Hey y’all,
We just finished a successful migration of omnibus gitlab 13.5 from an old centOS 6 server to centOS 8.
We followed all the backup and restore documentation, and everything worked as we expected it to; including LDAP, emails, gitlab ci tokens and whatnot, which surprised us!
However, none of the packages (maven, nuget) made it from the old server to the new one. We could see the packages listed but there was nothing server-side to pull/download.

After manually copying over all the packages (and verifying permissions) all is fine with the package registry, but now we are wondering how to avoid this in the future, and how to make our scheduled backup include our packages?

Any insights?