Thanks! We had some interest in running Javalin on GraalVM in the past, but no one has updated the tutorial in many years. It used to work though, so I bet it still would, if you really wanted it to.
My concern would be around reflection, which I think you said gets used when running with virtual threads? and which native compilation can't handle easily. It may need a Quarkus-like pre-build step to generate glue code to work round it.