TLDR

Update the annotation to be kubernetes.io/ingress.class: public

Why

For MicroK8s v1.21, running

microk8s enable ingress

Will create a DaemonSet called nginx-ingress-microk8s-controller in the ingress namespace.

If you inspect that, there is a flag to set the ingress class:

      - args:
        ... omitted ... 
        - --ingress-class=public
        ... omitted ... 

Therefore in order to work with most examples online, you need to either

1. Remove the --ingress-class=public argument so it defaults to nginx
2. Update annotations like kubernetes.io/ingress.class: nginx to be kubernetes.io/ingress.class: public