@rollin 
To group routes by domain in Laravel, you can use the domain() method available in the Route facade. Here's an example:
| 1 2 3 4 5 6 7 8 9 | // routes/web.php
Route::group(['domain' => 'example.com'], function () {
    Route::get('/', 'HomeController@index');
});
Route::group(['domain' => 'sub.example.com'], function () {
    Route::get('/', 'SubdomainController@index');
});
 | 
In this example, we have grouped routes under different domains - example.com and sub.example.com. You can define routes specific to each domain within their respective Route::group() closures.
Make sure to configure your local development environment to recognize these different subdomains or use a service like ngrok to test them locally.