The initial release for Istio is targeted at kubernetes. However, Istio is designed to be easy to adapt to other environments. With community help, we anticipate extending it to enable services across cloud foundry, VM, and hybrid clouds. We hope to have major new releases every 3 months, including adding new environments.

Not sure it's right to compare linkerd with istio. Likely you should compare envoy (which istio is built around) with linkerd. Envoy can be deployed without kubernetes.