route/web.php
Auth::routes();
Route::get('/home', 'HomeController@index')->name('home');
Route::group(['prefix' => 'admin'], function () {
    Voyager::routes();
Route::get('/welcome', 'Welcome');
app\Http\Controllers\Welcome.php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
class Welcome extends Controller
     * Handle the incoming request.
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
    public function __invoke(Request $request)
        return view('welcome');
          
I discovered the cause of the problem
https://github.com/the-control-group/voyager/blob/4b6b3a3f7cf30abc1220c503a12858d41c653486/src/Listeners/AddBreadMenuItem.php#L32

This is incorrect mrthod for require routes!
Just check RouteServiceProvider in Laravel:

https://github.com/laravel/laravel/blob/2a483bbf60566cab6fbd0340fb3877fc09889bc3/app/Providers/RouteServiceProvider.php#L54-L56
Route::middleware('web')  - set group for routes

->namespace('App\Http\Controllers') - set namespaces for controllers!!!

->group(base_path('routes/web.php')); - require routes!
          
@Sylk The issue is still active so I don't think this should be closed. I'm experiencing the same thing and it's really annoying.
@Xmk Pointed out the issue - but it doesn't seem like it was fixed or addressed yet. Honestly from my local testing it seems like line 32 should just be removed.
https://github.com/the-control-group/voyager/blob/4b6b3a3f7cf30abc1220c503a12858d41c653486/src/Listeners/AddBreadMenuItem.php#L32
It doesn't seem to do anything other than cause this error to be thrown. After removing that line, the Bread creation worked as expected and a Menu item was added.
      
* Fix issue #3623
The line I'm removing is the cause of #3623. Once removed the BREAD creation seems to work as expected, however with it included it just causes exceptions to be thrown.
* Remove whitespace to make StyleCI happy