RegistryUI uses "projects" to define access to Docker Registry repositories. A project defines users and groups that are authorized to access a repository. Without a defined project, users have no access to a repository, even if the repository exists in the Docker Registry. Authorized users and groups can be defined when creating a project.
Projects can be defined by an administrator using the Repositories, Projects and Tags Explorer. The List tab of the Repositories, Projects and Tags Explorer shows Docker Registry repositories even if no project has been defined yet.