We use Sonatype Nexus OSS to host private as well as mirror public Maven, npm, and Docker repositories. It took a small amount of fiddling but in less than a day we were up and running, using our LDAP for auth, and it’s been pretty much trouble free from the get go. In fact, we even use it to host our own completely custom internal package system (based on Ivy) for our content packages and database modules. It’s been a huge boon to us.

Artifactory is another competitor but last I checked npm and Docker registries required the paid version.