The kubernetes_manifest resource can be used to create any Kubernetes API resource, including custom resource definitions. See the provider documentation page for more information on the additional attributes available for this resource.
Argo CD is an extremely popular declarative, GitOps-based continuous delivery tool. It is an open source tool and part of the Cloud Native Computing Foundation (CNCF). It is effortless to install and set up, and it offers various features and a jazzy UI to manage all your application requirements.
Developers are accustomed to using their own tooling and writing in familiar languages.