Looks like official JDK 21 eclipse-temurin Docker images are up! Updating the clojure images now (will take a bit for all of the various PRs to get approved and automations to flow through and build). But later today or tomorrow the images should appear on Docker Hub!
And since 21 is a new LTS release, that will become the new default if you don't specify a JDK version in your clojure image tags