Hey Kurt, thanks so much for the question! Really it comes down to context and location. Istio is a great mechanism for microservices running within Kubernetes to find other microservices. Function Router helps front ends, which more than likely aren't running inside Kubernetes, find API endpoints backed by Functions-as-a-Service running on edge devices.

If we got to the point where we'd be running Kubernetes on an ISR4K in a way that exposed API endpoints, then there'd be more overlap but for how that's the distinction between the two.