This allows to pass an annotation selector to mate which will instruct it to filter services and ingresses based on that. This allows for numerous possibilities to opt-in to being processed by different dns controllers and versions.

For example, calling mate with

./mate \
  --producer kubernetes \
  --kubernetes-filter external-dns.kubernetes.io/controller=mate/v1 \
  [...]

will allow it to play well with other dns controllers. Cluster users can annotate their service according to the agreed upon annotations and opt-in to have their service processed by mate.