As others mentioned, that command relies on the proxy having an external IP. Local Kubernetes distributions usually will not configure networking and cluster configuration for LoadBalancer Services automatically, but most provide plugins that you can use to provision external IPs on a local network interface, e.g.
You can alternately use kubectl port-forward to access the proxy without a LoadBalancer, in which case you’d reach it over localhost.
When using the ingress controller, you typically do not use the Kong admin API to configure your routes and services. You instead create Kubernetes Ingress and Service resources, and the controller will translate them into Kong configuration on your behalf, as shown in our getting started guide.
When using a database, you can create routes and services directly via the admin API if you expose it (using port-forward is probably the simplest means to access the admin API with your environment). This configuration can coexist with controller-managed configuration, but we typically don’t recommend mixing manually-managed and controller-managed configuration. Unless you have a known reason you cannot manage part of your configuration via the controller (for example, it doesn’t support Kong Enterprise Developer Portal configuration), you should manage configuration entirely through Kubernetes resources.