Rename the file smallrye-mutiny-vertx-service-discovery-backend-redis-3.5.0-javadoc.jar to smallrye-mutiny-vertx-service-discovery-backend-redis-3.5.0-javadoc.zip
Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder smallrye-mutiny-vertx-service-discovery-backend-redis-3.5.0-javadoc
Double click index.html will open the index page on your default web browser.