I might be wrong but I think you are facing a challenge with k8s (or k3s specifics) rather than a problem with the operator itself.
From the error message, my assumptions is that you tweaked
operator.yaml and added a pullsecret: "pulumi-kubernetes-operator" which points to a secret that does not exists in the default namespace.
`kubectl get secrets`should confirm.
Now my other assumption is that because you are using k3s in an isolated environment so you need to pull the image from somewhere else than dockerhub (which is the default for the image: pulumi/pulumi-kubernetes-operator:v1.8.0)
In that case using a local registry would force you to the following steps:
1. Create the registry if not already
created by k3s bootstrap
2. Create the
pullSecret in any namespace you need to pull the images (or globally)
3. Use this secret in the field pullSecret in the deployment manifest.