GKE removed the built-in gcp auth provider from kubectl and client-go, so any kubeconfig still using auth-provider gcp fails - inside k9s too. Install gke-gcloud-auth-plugin with gcloud components install, then regenerate the kubeconfig entry using gcloud container clusters get-credentials. k9s picks up the new exec-based auth and connects.

## The error
```text
error: The gcp auth plugin has been removed. Please use the "gke-gcloud-auth-plugin" kubectl/client-go credential plugin instead.
See https://cloud.google.com/blog/products/containers-kubernetes/kubectl-auth-changes-in-gke for further details.
```

## What to do
1. Install the plugin:
```bash
gcloud components install gke-gcloud-auth-plugin
```
   Expected: Plugin installs.
2. Regenerate the kubeconfig entry:
```bash
gcloud container clusters get-credentials [cluster] --region [region] --project [project]
```
   Expected: Kubeconfig rewritten with the exec plugin entry.
3. Verify with kubectl:
```bash
kubectl get pods
```
   Expected: Works, no gcp plugin error.
4. Restart k9s.
   Expected: Connects to the GKE cluster.

## When this applies
- the exact gcp auth plugin has been removed message
- GKE kubeconfigs created before the auth change
- kubectl 1.26+ and k9s against GKE

## When it does NOT apply
- gke-gcloud-auth-plugin executable not found (install the plugin first)
- non-GKE clusters

## Works with
kubectl 1.26+, k9s, gke-gcloud-auth-plugin, Google Cloud SDK

### WARNING: the gcp auth plugin is deprecated
Earlier warning for the same change. Migrate the same way before it becomes the error.

## Why it happens
Google moved GKE kubectl auth from an in-tree gcp provider to the external gke-gcloud-auth-plugin exec plugin. Old kubeconfig entries reference the removed provider, and newer clients refuse them.

## Edge cases
- Setting USE_GKE_GCLOUD_AUTH_PLUGIN=True was the transitional workaround; the durable fix is regenerating the config entry.
- Delete the stale config (or back it up) before regenerating if kubectl keeps reading the old entry.

## Resolved from
dev.to GKE kubectl auth guide - https://dev.to/meddlesome/kubectl-authentication-error-on-gke-v126-58ba