Service don't have clusterIP, and lowable-workflow-ui is not accessable

Start by rendering the Flowable Helm chart with the posted host, ingress, and PostgreSQL values, then compare the generated UI Service and Ingress with the manifests shown in the issue. Trace how the UI Service selector, service type, and ingress hostname are configured. Done means the rendered configuration routes workflow.mydomain.xxx to the UI successfully.

This is what I modified to my value

host:
  external: workflow.mydomain.xxx
ingress:
  class: "nginx"
  useHost: true
postgres:
  storage:
    storageClassName: "microk8s-hostpath-retain"

It successfully installed, but I found flowable-workflow-flowable-ui service's clusterIP is None:

kind: Service
apiVersion: v1
metadata:
  name: flowable-workflow-flowable-ui
  namespace: workflow
  uid: 60c3abd3-4284-42bb-add8-42b7be8426d4
  resourceVersion: '3731938'
  creationTimestamp: '2023-11-27T09:56:39Z'
  labels:
    app.kubernetes.io/instance: flowable-workflow
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: ui
    helm.sh/chart: flowable-6.8.0
  annotations:
    meta.helm.sh/release-name: flowable-workflow
    meta.helm.sh/release-namespace: workflow
  managedFields:
    - manager: kubeapps-apis
      operation: Update
      apiVersion: v1
      time: '2023-11-27T09:56:39Z'
      fieldsType: FieldsV1
      fieldsV1:
        f:metadata:
          f:annotations:
            .: {}
            f:meta.helm.sh/release-name: {}
            f:meta.helm.sh/release-namespace: {}
          f:labels:
            .: {}
            f:app.kubernetes.io/instance: {}
            f:app.kubernetes.io/managed-by: {}
            f:app.kubernetes.io/name: {}
            f:helm.sh/chart: {}
        f:spec:
          f:clusterIP: {}
          f:internalTrafficPolicy: {}
          f:ports:
            .: {}
            k:{"port":8080,"protocol":"TCP"}:
              .: {}
              f:name: {}
              f:port: {}
              f:protocol: {}
              f:targetPort: {}
          f:selector: {}
          f:sessionAffinity: {}
          f:type: {}
spec:
  ports:
    - name: http
      protocol: TCP
      port: 8080
      targetPort: 8080
  selector:
    app.kubernetes.io/instance: flowable-workflow
    app.kubernetes.io/name: flowable-workflow-ui
  clusterIP: None
  clusterIPs:
    - None
  type: ClusterIP
  sessionAffinity: None
  ipFamilies:
    - IPv4
  ipFamilyPolicy: SingleStack
  internalTrafficPolicy: Cluster
status:
  loadBalancer: {}

And I can't access it from https://workflow.mydomain.xxx , why?