Because we use plantuml for creating of diagrams, it is important, that a plantuml server is running. Currently the system is configured to use a local plantuml server when building locally.
You can start a server using a docker container
docker run -d -p 9080:8080 plantuml/plantuml-server:jetty
Then you are able to generate the documentation
antora site-workspace.yml
or if you want to include all versions
antora site-workspace-full.yml