We are releasing garnix modules today.
If you try it out, you’ll see that on the surface it feels a lot like PaaSs such as Render, Railway, and Fly.io. You pick a stack and a repo, give some basic details about it, and garnix builds and tests your software, and optionally spins up your servers.
But unlike those other services, it has a lot of the benefits we know from Nix, such as great caching, easy local reproducibility, a ton of packages, and easy rollbacks. That’s because under the hood, it is Nix. More specifically, it’s a module system (like NixOS modules) that provides options for various stacks; but unlike existing module systems, it’s designed to work well with HTML forms. So you can provide all the arguments without touching Nix files. In the end, we can generate a pull-request to you repo that captures the choices you made into a flake file, so the configuration is in version control.
Here’s a short video demoing it: 
The module code is open source, and is extensible with newer modules. If you’d like to collaborate on developing new ones, get in touch!