If you are looking to deploy a laravel app in railway app. Check out this post

I recently deployed a laravel app in railway app and noticed that the asset files (css, images) were not loading which put off the designs of the app. Then i realized that the reason for this behaviour was because the app was trying to fetch the asset from "http" url while the main application was hosted in an "https" url. To solve this issue i updated the boot method of the class AppServiceProvider in App\Providers\AppServiceProvider.php to enforce the https scheme. Below is the code snippet that worked for me.

public function boot()
{
    if($this->app->environment('production')) {
        \URL::forceScheme('https');
    }
}

I also googled and found that you can use secure_asset to fetch the assets instead of just asset. I haven't tried this but looks like it'll work

<link href="{{ secure_asset('assets/mdi/css/materialdesignicons.min.css') }}" media="all" rel="stylesheet" type="text/css" />