This could be tricky: not only you need a Maven repository proxy/cache which will allow Maven to access and download Vaadin jars (and transitive dependency jars), you also need a (p)npm proxy/cache which will allow (p)npm to access and download JavaScript client-side stuff used by Vaadin.

Tips for Maven repository proxy/caches:

• Tiny Maven Proxy looks simple and extremely useful
• Nginx could also work
• Sonatype Nexus used to be good but now it looks enterprisey
• JFrog Artifactory - perhaps you’ll manage to download and run it locally

Tips for (p)npm proxies/caches:

• Verdaccio
• Using Nexus as npm proxy cache is possible too
  • Perhaps the docker-nexus-npm-registry could help.

Using Vaadin Licenses in offline mode:

• See licensing FAQ
• Pass the license via a JVM parameter to Maven via -Dvaadin.proKey=your@email.com/uuid