Java 11 plugins use registry.redhat.io/codeready-workspaces/plugin-java11-rhel8:2.1 image which provides Gradle support.
It makes sense to set GRADLE_HOME environment variable into these plugins to say Java Language Server to use local installed Gradle instead of downloading it.
It also makes possible to use devfiles with java11 plugin in disconnected environment.

As a result each plugin inside https://github.com/redhat-developer/codeready-workspaces/tree/master/dependencies/che-plugin-registry/v3/plugins/redhat/java11 folder should contain:

      env:
      - name: GRADLE_HOME
        value: /opt/gradle/