The latest release version is 2.8.3 from October 2023. See NewFeatures283 for a full list of improvements compared to the previous version. A Java 8 JVM and a Servlet 3.1 container is required.
If you want to use the as-yet-unreleased features mentioned in NewFeaturesTrunk, you'll have to download the source code and build the war file yourself.
This version is for JakartaEE 10; as such it needs Java 11 and Tomcat 10.1 to run on. Its functionality is on a par with 2.8.3, plus everything mentioned in NewFeaturesTrunk. It is functional, but has not had as much testing as previous versions of JForum. Let us know if you notice anything unusual.