nixpkgs has many owners that span across the 80,000+ software packages. When you open a PR against a specific package, the owner is notified via CI that Nix Foundation runs.

To test with your own config, it's easy to instead of importing nixpkgs, to import nixpkgs.applyPatches { patch } with a path to your fix.

And yes, overlays are a great way to quickly override attributes from a package definition, maybe while waiting on others to fix upstream ;)