Just want to add additional info here
default- prefix is refers to what k8s namespace the middleware manifest is deployed to. If it is deployed in kubernetes default namespace, of course the prefix will be default-. But if you deploy middleware manifest into abcde namespace, the prefix will be abcde-
Just found about this info in How to configure middleware with kubernetes-ingress? (middleware "xyz" does not exist) - #8 by sw360cab - Traefik v2 (latest) - Traefik Labs Community Forum