Universal Containers CUC) has been on the org development model with scratch orgs are already...

To move to the package development model, the administrator must enable both the Dev Hub and the Second-Generation Managed Packages in setup. The Dev Hub is the main org where the administrator can create and manage scratch orgs and packages. The Second-Generation Managed Packages are the new format of packages that support modular development and versioning. The Unlocked Packages are a type of second-generation packages that are not tied to a namespace and can be installed and customized in any org. The Source Tracking for Scratch Orgs is a feature that allows the administrator to track the changes made in a scratch org and push or pull them to or from a source repository.