Keycloak 17 - cannot create realm with java client

I want to create a new realm via the java client.
Here is my code - its pretty simple - I use the quarkus keycloak client (quarkus-keycloak-admin-client)

public class InitKeycloak {

    private static final String serverUrl = "http://localhost:8099/";
    private static final String realm = "master";
    private static final String username = "admin";
    private static final String password = "admin";
    private static final String clientId = "admin-cli";
    private static final String appRealmName = "test";

    public void createSimpleRealm() {

        RealmRepresentation realm = new RealmRepresentation();

        Keycloak keycloak = KeycloakBuilder
                .resteasyClient(new ResteasyClientBuilderImpl().connectionPoolSize(10).build())


keycloak 17 is running in a local docker container.

docker run -d -p 8099:8080 -e KEYCLOAK_ADMIN=admin -e KEYCLOAK_ADMIN_PASSWORD=admin start-dev

The code is executed in a quarkus 2.7.1 project.

In Quarkus I get an HTTP 500 and in Keycloak I see the following error:

2022-02-18 09:54:26,562 ERROR [] (executor-thread-44) Uncaught server error: java.lang.NullPointerException
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(
        at java.base/java.lang.reflect.Method.invoke(
        at org.jboss.resteasy.core.MethodInjectorImpl.invoke(
        at org.jboss.resteasy.core.MethodInjectorImpl.invoke(
        at org.jboss.resteasy.core.ResourceMethodInvoker.internalInvokeOnTarget(
        at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTargetAfterFilter(
        at org.jboss.resteasy.core.ResourceMethodInvoker.lambda$invokeOnTarget$2(
        at org.jboss.resteasy.core.interception.jaxrs.PreMatchContainerRequestContext.filter(

Can you give me a hint whats going wrong? I checked several test suites where you do the same …
Reading stuff (like realm details) works - but the realm creation fails …

Thanks Max

Getting a very similar error when trying to create the realm from an export using the REST-api -

(using curl & co like shown in the examples here -

When importing the realm-export via Web-UI - everything works fine…

I think the minimum viable realm is