I'd like to use terraform to setup the EKS cluster, but then use Pulumi in place or helm or kustomize

Why not use Pulumi for both?

Because we're kind of used to creating and managing our infrastructure with Terraform

The switch to Pulumi should be easy 🙂 Just saying, the choice is yours ofc.

I guess you are looking for the

kubernetes

provider. Creating an instance of it on your own with a provided kubeconfig let’s you talk to the cluster to deploy manifests, locally templated helm charts or pulumi kubernetes objects defined inline. But as @tall-librarian-49374 mentioned, there is more to it. In most cases you need additional stuff for your kubernetes manifests like `loadBalancerIP`s,

resourceGroup

names for lookups, credentials for managed databases or secrets to create service accounts with additional permissions. All of this can become a mess if created externally and handed into pulumi as a config and is really way more convenient if created from pulumi directly.