Unable to self sign certificate nginx ingress k3s

I'm new to K3s, and have struggle with this step for a few days.

Environment: Ubuntu 20.04 | K3s installation without Traefik.

K3s installation script:

curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="server --no-deploy=traefik" sh -s -

Nginx ingress installation script

helm repo add nginx-stable https://helm.nginx.com/stable
helm repo update
helm install my-release nginx-stable/nginx-ingress

Cert-manager installation script

helm repo add jetstack https://charts.jetstack.io
helm repo update
helm install \
  cert-manager jetstack/cert-manager \
  --namespace cert-manager \
  --create-namespace \
  --version v1.3.1 \
  --set installCRDs=true

Verified with Cert-manager verifier

Create a testing namespace to play with kubectl create ns practice-cls

Test service deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: kuard
  namespace: practice-cls
spec:
  selector:
    matchLabels:
      app: kuard
  replicas: 1
  template:
    metadata:
      labels:
        app: kuard
    spec:
      containers:
        - image: gcr.io/kuar-demo/kuard-amd64:1
          imagePullPolicy: Always
          name: kuard
          ports:
            - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: kuard
  namespace: practice-cls
spec:
  ports:
  - port: 80
    targetPort: 8080
    protocol: TCP
  selector:
    app: kuard

Issuer

apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: selfsigned-cluster-issuer
  namespace: cert-manager
spec:
  selfSigned: {}

service ingress

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: kuard
  namespace: practice-cls
  annotations:
    cert-manager.io/cluster-issuer: "selfsigned-cluster-issuer"
spec:
  tls:
  - hosts:
    - example.example.com
    secretName: quickstart-example-tls
  rules:
  - host: example.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: kuard
            port:
              number: 80
  ingressClassName: nginx

# kubectl describe ing kuard -n practice-cls

Name:             kuard
Labels:           <none>
Namespace:        practice-cls
Address:          10.227.224.141
Default backend:  default-http-backend:80 (<error: endpoints "default-http-backend" not found>)
TLS:
  quickstart-example-tls terminates example.example.com
Rules:
  Host                 Path  Backends
  ----                 ----  --------
  example.example.com  
                       /   kuard:80 (10.42.0.76:8080)
Annotations:           cert-manager.io/cluster-issuer: selfsigned-cluster-issuer
Events:
  Type     Reason                     Age   From                      Message
  ----     ------                     ----  ----                      -------
  Warning  AddedOrUpdatedWithWarning  6m9s  nginx-ingress-controller  Configuration for practice-cls/kuard was added or updated ; with warning(s): TLS secret quickstart-example-tls is invalid: secret doesn't exist or of an unsupported type

I don't know if there was anything wrong with this, the kuard image was just a tutorial service from cert-manager. And I got ERR_SSL_UNRECOGNIZED_NAME_ALERT from the manifests above.

Let me know if there's some more information to troubleshoot this.

Thank you guys

After a while searching and experiment, I manage to handle this by:

Using K8s nginx ingress instead of the official one provide by nginx themself

Enable SSL passthrough either by editing the deployment of nginx controller or enable that right when installing