External DNS: Configure it in all namespaces

I have successfully installed external-dns in my Kubernetes cluster following the official steps on github, it creates a Route53 record and I am able to access it correctly. I installed this on a specific namespace.

My question is, do I need to deploy external-dns on each namespace (and then creating the service account, cluster role binding and deployment) or I can use the same deployment across namespaces?

The answer is no, you don't need to deploy it more than once. If you don't specify a namespace in the args section of your external-dns deployment using --namespace=, it works for all of the namespaces in the cluster.