Have you looked at using a caching proxy or maven repo in front of GitLab? For our TeamCity builds we have ProGet sitting in front of the public NuGet and Maven

Have you looked at using a caching proxy or maven repo in front of GitLab? For our TeamCity builds we have ProGet sitting in front of the public NuGet and Maven repos, it caches the downloads so any machine on our local network can reuse them instead of downloading artifacts every time.