I don’t know about Ansible within terraform, but I use them together for non-container infra. Terraform for deploying the actual VMs and other stuff, and Ansible for post deployment OS/application provisioning. Using them this way has been extremely flexible and easy to maintain. I also provision AMIs this way with Packer calling an Ansible playbook to set everything up. The beauty of that is you can run that same playbook on already provisioned VMs to keep them in sync too.