It's a setup application for libGDX that Just Works with Gradle 5.4.1, and so Just Works with Java 8-12 (at the least), and so should be a useful way to make new projects, especially for first-time libGDX users. This release is a minor improvement for some users, but is important if you develop LWJGL3 projects on MacOS. Before, the critical -XstartOnFirstThread argument was missing when the Gradle lwjgl3:run task was executed, which caused no problems on Windows or Linux, but blocked the task from running on MacOS. This is fixed. The version of Gradle in generated projects is now 5.4.1 instead of 5.4 . Generated files use tabs for indentation, which are more agreeable to more users than the previous mix of 2-space and 4-space indentation.
You use this much like the other setup jars: assuming you have Java installed (AdoptOpenJDK is recommended), you can run gdx-liftoff-1.9.9.2.jar like any other jar on your OS, and plug in the project name, project package, main class name, project directory, etc. Make sure to check any platforms you want to target; LWJGL3 or "new desktop" is recommended for all projects and is selected by default because it makes it easier to debug. Android is also selected by default and you can uncheck it if you don't intend to target that mobile OS. You can add optional JVM language support; Kotlin should be up-to-date in the 1.3.x branch but other languages are probably going to need updating in your project yourself. You can add various official and third-party extensions (third-party libraries) from the big lists on other tabs, and choose a different starting sample project template if you want. The Advanced tab lets you choose a different minimum JVM level (1.7 is safest for Android, but desktop-only can be 11 or 12 easily), a different libGDX version, and so on; most of the defaults are probably fine to stay with unless you want to use Java 8's Streams and lambdas, which would mean switching Java version to 1.8; a quirk of the naming convention means the setup can't generate projects that need Java 10 or newer, but you can configure that in the generated projects if you are sure users will have that version. When you're ready, press Generate; it's much faster than the official setup for various reasons. You should import the build.gradle file in your chosen project directory in your IDE of choice; the rest of usage follows the libGDX documentation.
I hope this can be useful!