Tried various annotations including the following one (based on https://artifacthub.io/packages/helm/ingress-nginx/ingress-nginx#additional-internal-load-balancer). But the load balancer which is intended to be internal is created for Service ingress-nginx-controller-internal as Internet-facing (but supposed to be Internal) in AWS each time:
controller:
service:
external:
enabled: true
...
internal:
enabled: true
annotations:
service.beta.kubernetes.io/aws-load-balancer-scheme: "internal"
service.beta.kubernetes.io/aws-load-balancer-backend-protocol: http
service.beta.kubernetes.io/aws-load-balancer-cross-zone-load-balancing-enabled: 'true'
service.beta.kubernetes.io/aws-load-balancer-type: nlb