GraalVM is really more like a very specialised JVM that can be used to spit out a native binary for any platform for which there exists a GraalVM version.

But in order to do that, it does some interesting things under the hood, and it doesn't play nicely with reflection by default (amongst other things). For some non-Java JVM languages that's a major problem since their compiler produces JVM byte code that relies heavily on reflection (Groovy is/was a great example of this). I'm unsure how much, if any, reflection Clojure relies on but that would be the most likely reason for it to struggle with GraalVM compatibility.

Well, the reason behind all that is that Graal has a closed-world assumption regarding classes - it has to know about every class file that will potentially get loaded at runtime.

SubstrateVM (which is what everyone here means when they say ‘GraalVM’) is not a compliant JVM, except for a get-out that just runs a normal JVM as a launcher.

Clojure is compatible. GraalVM is not compatible.