NixOS - neovim plugins

Hello,

The NixOS community has been great in helping me with my first steps in this distro. So I'll ask again few neovim-related issues I couldn't figure out after 3 days of search.

First, let me tell you that I'm trying to import a working neovim setup from another distro. Then let's see how I've configured neovim. I have this in my home.nix file:

programs.neovim = {
  enable = true;
  withPython3 = true;
  extraPython3Packages = (ps: with ps; [
    pynvim
    unidecode
    black
    isort
  ]);
  plugins = with pkgs.vimPlugins; [
    { plugin = *plugin_name*;
    type = "lua";
    config = builtins.readFile *config_file_path*;
    }
    ...
    ];
};

(my init.lua file is in the $HOME/.config/nvim folder)

With that most of my plugins work. Most because few are troublesome. Let's focus on three of them:

1. I have pkgs.vimPlugins.nvim-comment installed but neovim reports that the command CommentToggle is not an editor command

2. I have pkgs.vimPlugins.nvim-treesitter installed but the command TSInstall markdown returns "could not create parser dir '/nix/store/.../nvim-treesitter/parser ': Vim:E739: read-only file system '"

3. I have pkgs.vimPlugins.mason-nvim and pkgs.vimPlugins.mason-lspconfig-nvim installed but runngin checkhealth mason returns few warnings:

• mason.nvim is not the latest version (I use the unstable channel)
• pip: not available spawn: python3 failed with exit code 1 and signal 0. /run/current-system/sw/bin/python3: No module named pip (note that python3_host_prog and python3_host_prog pip are marked "OK")

Thanks again for your assistance.