https://docs.aws.amazon.com/codeartifact/latest/ug/external-connection.html lists public repos that can be added as external repositories.
How can I add an unlisted repo to my CodeArtifact, e.g. Clojars?
Note:
- Clojars for humans: https://clojars.org
- Clojars packages: https://repo.clojars.org.
Currently, CodeArtifact does not support connecting to arbitrary public repositories which are not on the list you mention.
That said, if you give that page a refresh you'll now find Clojars on the supported list!