This is an almost identical version of the NixOS configuration that I use.

Elements such as usernames are generalized; These kinds of values needs to be defined before using the configuration.
Reading and editing (if necessary) every file before using this configuration is highly recommended.

The configuration is split into various nix modules that are imported in configuration.nix.
configuration.nix
We can comment/uncomment modules to enable/disable them.  
 

This is very important.
In the Nix.nix file, you will find the stateVersion = "23.11"; value.
Nix.nix
The version should only be changed if you have installed NixOS from another version.
You should never need to change it afterwards, unless you re-install from a newer version.
For more information, please read more here.
NixOS options - system.stateVersion  
 

Using this configuration on a clean installation of NixOS will result in errors.
This is because Home Manager and unstable packages are defined but not present on the system.
If we do not use one or all of them, we can safely disable them.
The following section will explain how to add them, as well as where they can be enabled/disabled.
It will also show some other functionalities that can be enabled/disabled.  
 

Home Manager can be enabled/disabled by un/commenting the <home-manager/nixos> import in configuration.nix.
configuration.nix

It can be configured in the Home-Manager.nix module.
Home-Manager.nix

• Run this command to add the Home Manager channel.

sudo nix-channel --add https://github.com/nix-community/home-manager/archive/release-24.05.tar.gz home-manager

• Run this command to update the channels.

sudo nix-channel --update

Unfree packages can be enabled/disabled by un/commenting the Nixpkgs-unfree.nix import in configuration.nix.
configuration.nix

They can be configured in the Nixpkgs-unfree.nix module.
Nixpkgs-unfree.nix  
 

Unstable packages can be enabled/disabled by un/commenting the Nixpkgs-unstable.nix import in configuration.nix.
configuration.nix

They can be configured in the Nixpkgs-unstable.nix module.
Nixpkgs-unstable.nix

• Run this command to add the unstable channel.

sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos-unstable

• Run this command to update the channels.

sudo nix-channel --update

To use an unstable package, replace pkgs with pkgs.unstable in the relevant places.  
 

Use of Flatpak packages can be enabled/disabled by un/commenting the Flatpak.nix import in configuration.nix.
configuration.nix

They can be configured in the Flatpak.nix module.
Flatpak.nix

• Run this command to add the Flathub repository for the entire system.

flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo

• Run this command to add the Flathub repository for the current user.

flatpak remote-add --if-not-exists --user flathub https://dl.flathub.org/repo/flathub.flatpakrepo

Support for AppImages can be enabled/disabled by commenting the AppImage.nix import in configuration.nix.
configuration.nix

They can be configured in the AppImages.nix module.
AppImages.nix  
 

The main module contains more the Hyprland Wayland compositor and various other utilities.

The Hyprland desktop can be enabled/disabled by un/commenting the Hyprland-deskop.nix import in configuration.nix.
configuration.nix

It can be configured in the Hyprland-desktop.nix module.
Hyprland-desktop.nix  
 

• Single user
• Personal computing
• Desktops and laptops  
   

• Legacy BIOS
• Secure Boot
• Accessibility
• Touchscreen
• NVIDIA PRIME
• Remote desktop
• Snap packaging system
• Use in most virtual machines (with Hyprland)
• Computers with:
  • A non-x86_64 (AMD64) CPU architecture
  • No adequate GPU acceleration
  • Less than 4 GiB of RAM (Swap might be heavily used with less)
  • Less than 128 GiB of storage (Some Nix storage optimizations are already enabled)  
     

The ST Flexipatch project.
ST Flexipatch GitHub

The version I use can be found in this directory.
./Programs/ST/

Help is available in:

• The configuration.nix(5) man page
• The on-device manual by running the nixos-help command
• The online manual
  Online manual
• The NixOS Wiki
  NixOS Wiki

A searchable list of available packages for NixOS can be found here.
NixOS package search
Alternatively, we can use nix search in a terminal.

A searchable list of available options for NixOS can be found here.
NixOS options search