Out of the box Marginalia enriches package completion with information from the built-in package manager. This packages teaches it to additionally use the Epkgs database, and if the Borg package manager is available, then it uses information provided by that as well.
(with-eval-after-load 'marginalia
(setcar (alist-get 'package marginalia-annotator-registry)
#'epkg-marginalia-annotate-package))
