Unable to access RabbitMQ UI

I deployed RabbitMQ in Kubernetes with the manifest below.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: rabbitmq
  namespace: X 
spec:
  serviceName: rabbitmq
  selector:
    matchLabels:
      app: rabbitmq
  template:
    metadata:
      labels:
        app: rabbitmq
    spec:
      containers:
      - name: rabbitmq
        image: rabbitmq:v01
        ports:
          - containerPort: 15672
            name: rabbitmq
          - containerPort: 5672
        env:
          - name: RABBITMQ_DEFAULT_USER
            value: "..."
          - name: RABBITMQ_DEFAULT_PASS
            value: "..."
        livenessProbe:
          tcpSocket:
            port: 5672
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          tcpSocket:
            port: 5672
          initialDelaySeconds: 10
          periodSeconds: 5
---
apiVersion: v1
kind: Service
metadata:
  name: rabbitmq
spec:
  ports:
  - port: 5672
    protocol: TCP
    targetPort: 5672
  selector:
    app: rabbitmq
---
apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
  name: rmq
  namespace: X
spec:
  entryPoints:
    - websecure
  routes:
  - match: Host(`Y`) 
    kind: Rule
    services:
    - name: rabbitmq
      port: 5672
  tls: {}

After applying this manifest I can see that my pod is running. But when I try to port forward I don't have access to RabbitMQ UI. I have the error 'internal server error' or 'bad gateway'.

In the logs of the pod I can see :

Server startup complete; 3 plugins started.
* rabbitmq_prometheus
* rabbitmq_web_dispatch
* rabbitmq_management_agent

In the logs I can see:

2023-06-05 21:23:36.319429+00:00 [info] <0.1006.0> accepting AMQP connection <0.1006.0> (IP1:34330 -> IP2:5672)
2023-06-05 21:23:36.319611+00:00 [error] <0.1006.0> closing AMQP connection <0.1006.0> (IP1:34330 -> IP2:5672):
2023-06-05 21:23:36.319611+00:00 [error] <0.1006.0> {bad_header,<<"GET / HT">>}

Where am I wrong ?

There are 2 issues with your manifests:

1. Your Service should be pointing to RabbitMQ's port 15672 for accessing UI as mentioned in this document instead of 5672.

2. Both Service and StatefulSet should be in same namespace. In your case they are in default and x respectively.