I suggest checking out Anemos (https://github.com/ohayocorp/anemos), the new boy in the town. It is an open source single-binary tool written in Go and allows you to use JavaScript/TypeScript to define your manifests using templates, object oriented approach, and YAML node manipulation.

You can read a comparison with Helm here: https://www.ohayocorp.com/anemos/docs/comparison/helm

P.S. I am the author of the tool.