Services inside kubernetes may use self signed certs but traefik does not connect to them. Instead, it will have an error inside in the traefik pod saying it cannot verify the certificate.

To allow insecure ssl create the serverTransport

apiVersion: traefik.io/v1alpha1
kind: ServersTransport
metadata:
  name: insecure-transport
  namespace: default
spec:
  insecureSkipVerify: true

Then to use it, in the ingress serversTransport: default-insecure-transport@kubernetescrd

for example

apiVersion: traefik.io/v1alpha1
kind: IngressRoute
metadata:
  name: wiki
  namespace: wiki
spec:
  entryPoints:
    - websecure
  routes:
    - match: Host(`wiki.projectkube.com`)
      kind: Rule
      services:
        - name: wiki
          port: 80
          serversTransport: default-insecure-transport@kubernetescrd

You may need to enable cross CRD in traefik

#kubernetes/traefik