I found this issue that talks about it, with a workaround But when I try to apply that yaml (after updating the domain name etc of course) I get

resource mapping not found for name: "tls-rancher-ingress" namespace: "cattle-system" from "fix.yaml": no matches for kind "Certificate" in version "<http://cert-manager.io/v1alpha2|cert-manager.io/v1alpha2>"
ensure CRDs are installed first