After I reinstalled laragon, then

λ php artisan db:seed
[Symfony\Component\Debug\Exception\FatalThrowableError]
Class 'User' not found

The code in DatabaseSeeder
$user = new User();

But it works as
$user = new \App\User();

I could not find the solution. php artisan could not work at
λ php artisan db:seed
λ php artisan make:migration (works at 5.5: php artisan migrate)
...