Better late than sorry, I just saw this post. The extension is also provided as Ruby gem, so you need to manage the Gem with gem-maven-plugin and mavengem-wagon, then configure the require pointing to the property path. There's an example using asciidoctor-revealjs https://github.com/asciidoctor/asciidoctor-maven-examples/blob/main/asciidoc-to-revealjs-example/pom.xml, simply replace the gem name.