renovate/lib/manager/kubernetes

The kubernetes manager has no fileMatch default patterns, so it won't match any files until you configure it with a pattern. This is because there is no commonly accepted file/directory naming convention for Kubernetes YAML files and we don't want to check every single *.yaml file in repositories just in case any of them contain Kubernetes definitions.

If most .yaml files in your repository are Kubernetes ones, then you could add this to your config:

{
  "kubernetes": {
    "fileMatch": ["\\.yaml$"]
  }
}

If instead you have them all inside a k8s/ directory, you would add this:

{
  "kubernetes": {
    "fileMatch": ["k8s/.+\\.yaml$"]
  }
}

Or if it's just a single file then something like this:

{
  "kubernetes": {
    "fileMatch": ["^config/k8s\\.yaml$"]
  }
}