does anyone know an REST-API to deploy a helm-chart, with specified project and namespace?
Helm isn’t going to know anything about a Project, that’s a purely Rancher construct (albeit a CRD). Namespace names are unique within a cluster though so if that already exists then that’s where your resources will be deployed. If it doesn’t exist, I would suggest creating the Namespace using kubectl then the Rancher CLI to create the Project and move the namespace under it, ahead of time. Then helm update blah … – install --force