Managing Kubernetes resources in Terraform: Kubernetes provider (opens in new tab)

You can use YAML files with kubernetes_manifest resources if you like, though you'll probably run into issues that the bespoke resources (e.g. kubernetes_deployment) handle for you.

You can also use https://github.com/gavinbunney/terraform-provider-kubectl.

Yeah that's definitely the way to go if there's already a helm chart. If it's just raw manifests I'd rather convert to HCL than build a helm chart to feed into TF, but that's just because I know TF better, most of my configuration is already there, so I'd prefer to keep abstraction boundaries small. But it's nice to have the options.