trypost/app/Providers/HorizonServiceProvider.php

<?php

declare(strict_types=1);

namespace App\Providers;

use Illuminate\Support\Facades\Gate;
use Laravel\Horizon\Horizon;
use Laravel\Horizon\HorizonApplicationServiceProvider;

class HorizonServiceProvider extends HorizonApplicationServiceProvider
{
    /**
     * Bootstrap any application services.
     */
    public function boot(): void
    {
        parent::boot();
    }

    /**
     * Register the Horizon gate.
     *
     * This gate determines who can access Horizon in non-local environments.
     */
    protected function gate(): void
    {
        Gate::define('viewHorizon', function ($user = null) {
            $allowedEmails = array_filter(
                array_map('trim', explode(',', config('horizon.allowed_emails', '')))
            );

            return in_array(optional($user)->email, $allowedEmails);
        });
    }
}