It is because it departs from POSIX that it is good; I recognize the syntax for some functionality is cumbersome and hard to remember though. There are similarities like command names and piping still…

I use NixOS and home-manager, so for switching I just

  home-manager.users.yuu = {
    programs.nushell = {
      package = pkgs-update.nushell;
      enable = true;
      configFile.source = ../../config/nushell/config.nu;
      envFile.source = ../../config/nushell/env.nu;  
    };
  };

The config.nu and env.nu is basically the default just with a customized prompt.

Then in my alacritty.ylm I set shell to the nu binary

shell:
  program: /etc/profiles/per-user/yuu/bin/nu

Also learned from official resources https://www.nushell.sh/book. When I have doubts, I ask either on Nushell’s GitHub discussions or https://matrix.to/#/#nushell:matrix.org

And to keep a POSIX shell

{
  environment = {
    systemPackages = with pkgs; [
      mksh
    ];

    sessionVariables = rec {
      TERM = "alacritty";
      TERMINAL = "alacritty";
      SHELL = "${pkgs.mksh}/bin/mksh";
    };

  environment.shells = [
    "${pkgs.mksh}/bin/mksh"
  ];
}