Traefik (v2.2) Ingress on Kubernetes: HTTP and HTTPS cannot co-exist
From the document of traefik/v2.2/routing/routers/tls, it says that " When a TLS section is specified, it instructs Traefik that the current router is dedicated to HTTPS requests only (and that the router should ignore HTTP (non TLS) requests). ".
That explains all what I have encountered.
My solution to this was to create two ingress routers, one for HTTP and another for HTTPS.