It's another release! Java 13 is out and now so is Gradle 6.0, which is the first version to support Java 13. This gdx-liftoff version defaults to Gradle 6.0, and though there's still no convenient way to choose language level 13 in the app, you can set it by changing sourceCompatibility in your desktop and/or lwjgl3 modules and core. It's still probably a good idea for some usage to use language level 7, which is what libGDX uses, but many projects can upgrade to level 8 at least. Java 9 and higher are, of course, not compatible with Android, iOS, or GWT.