Sorry, those are basically two different errors.

The original error was NU1101 ("error NU1101: Unable to find package NAME. No packages exist with this id in source(s): nuget, _nix") for Kaligraphy, Kanvas, Kompression, and Komponent.

CS0246 is from me trying to self-package Komponent, Kaligraphy, and Kanvas to provide the derivation.
(k2Repo in the following is just me trying to set the used src once in flake.nix and passing it to the derivations that way so I don't have to update the used commit info more than once)

{
  packages.x86_64-linux = {
    default = pkgs.callPackage ./package.nix { inherit k2Repo; komponent = self.packages.${system}.komponent; kaligraphy = self.packages.${system}.kaligraphy; kanvas = self.packages.${system}.kanvas; };
    komponent = pkgs.callPackage ./komponent.nix { inherit k2Repo; };
    kaligraphy = pkgs.callPackage ./kaligraphy.nix { inherit k2Repo; komponent = self.packages.${system}.komponent; };
    kanvas = pkgs.callPackage ./kanvas.nix { inherit k2Repo; komponent = self.packages.${system}.komponent; };
  };
};