See https://sourceforge.net/projects/hibernate/files/hibernate-search/5.8.0.Beta4/ , the module and its dependencies seem to be missing.
By the way, the Elasticsearch module is in the "optional" directory, which is a bit weird. Maybe we should work a bit on how the compressed archives are organized? => Actually, we already organize the optional dependencies as a tree. No idea why I said that.
Or, you know... Just drop this kind of distribution and add a mvn one-liner in our docs showing how someone can download a JAR they want and its dependencies.