Installation docs: What version of Kubernetes is required / recommended?

From https://development.open-match.dev/site/docs/installation/:

There are instructions on how to create a GKE cluster (and links to how to create minikube) but no indication of what version of Kubernetes should be used.

My suggestion (this is what we do for Agones) would be to pick a version and just suggest using that one. Use it in your CI and developer testing and that will give you confidence that it works. It also allows you to tailor your instructions based on a specific version of Kubernetes (e.g. https://github.com/googleforgames/open-match-docs/issues/84).