Split-View DNS with a single ingress controller?

[rowanmoul]

I know that I can do Split-View DNS with two ingress controllers using different ingress classes (and different ingress resources) and two instances of external-dns filtering on those classes (#3220).
It would be great if I could use a single ingress controller exposed both publicly and privately (see ingress-nginx addtional internal load balancer), and a single ingress object, but have the two instances of external-dns create different entries according to their configuration (in my case, one using azure private dns, and the other using azure public dns). In the most basic use-case this is possible, but it breaks down if I need to use annotations like external-dns.alpha.kubernetes.io/target on the ingress resource for the internal case, and not for the external case.
Is there no way to do this currently with external-dns?

[rowanmoul]

After working on this for a while longer, I realized I actually need to run separate ingress controller instances because I need to be able to expose certain things only on the internal network (but still with TLS provided by ingress-nginx + cert-manager).
However if I had been able to proceed with a single ingress controller what would have probably worked is running the azure-private-dns instance of external-dns with the service and crd sources only, and running the azure-dns (public) version of external-dns with the ingress source only. I would have then used CRs to configure my internal dns entries, all of which would be CNAME records pointing at the hostname defined for the internal nginx service.

In a more ideal case, there would be an --ignore-target-annotation flag that I could set on the public external-dns but such a flag does not exist.
Even better would be if all the basic annotations could be prefixed with the provider name such that they would be ignored by all other providers.