You are attempting to run with an unsupported Java Virtual Machine : Eclipse OpenJ9
Please visit https://adoptopenjdk.net and install the HotSpot variant.
OpenJ9 is incompatible with several of the transformation behaviours that we rely on to work.
Exception in thread "main" java.lang.IllegalStateException: Open J9 is not supported
	at cpw.mods.modlauncher.ValidateLibraries.validate(ValidateLibraries.java:33)
	at cpw.mods.modlauncher.Launcher.main(Launcher.java:63)