My laptop says otherwise lol and because you didnt read the links I put

services.xserver.videoDrivers = [
    "amdgpu"
    "nvidia"
  ];
hardware.nvidia.prime = {
    offload = {
      enable = true;
      enableOffloadCmd = true;
    };
    # Make sure to use the correct Bus ID values for your system!
    nvidiaBusId = "PCI:0:2:0";
    amdgpuBusId = "PCI:54:0:0";
  };

Is all it takes to install Nvidia Prime Offloading on a NixOS machine with AMD iGPU and an Nvidia dGPU.