How can I build this?

[UsrBinLuna]

Hey, I'm trying to compile this but it fails with

General error during conversion: Unsupported class file major version 65
  
java.lang.IllegalArgumentException: Unsupported class file major version 65

I've tried with Java 21 and 17, Gradle 7.2 and 8.6. All required dependencies are already included, any help is appreciated