OPA is very useful in many use cases, e.g. k8s as you wrote here, also good for linux, kafka, sql, terraform , etc.

Check out more, e.g. Rego playground, confest,

opa, gatekeeper, istio and vscode plugins, etc.. at my earlier post :

https://www.linkedin.com/posts/walterwlee_open-policy-agent-activity-6664356273871556608-V_PG/