Linkerd is not very similar to Etcd or Consul. It's a proxy that sits between your microservices/apps to act as a middleman for RPC calls. Being a proxy, it can handle things like load balancing, throttling and failure handling, meaning you don't have to build that into each app.

When used together with Kubernetes, Linkerd will use Kubernetes for discovery, so you don't need Etcd or Consul directly (K8s itself relies on Etcd, though).