This worked for me

<?php

namespace App\Filament\Pages\Auth;

use Coderflex\FilamentTurnstile\Forms\Components\Turnstile;
use Filament\Forms\Components\Field;
use Filament\Auth\Pages\Register as BaseRegister;
use Filament\Schemas\Schema;
use Illuminate\Database\Eloquent\Model;

class Register extends BaseRegister
{
    public function form(Schema $schema): Schema
    {
        return $schema
            ->components([
                $this->getNameFormComponent(),
                $this->getEmailFormComponent(),
                $this->getPasswordFormComponent(),
                $this->getPasswordConfirmationFormComponent(),
                $this->getTurnstileFormComponent(),
            ]);
    }

    protected function getTurnstileFormComponent(): Field
    {
        return Turnstile::make('cf-turnstile-response')
            ->label('Captcha Verification')
            ->size('normal');
    }

    protected function handleRegistration(array $data): Model
    {
        $user = parent::handleRegistration($data);

        // Auto-assign provider role
        $user->assignRole('provider');

        return $user;
    }
}

Hello,

is there any tutorial / how to about creating a custom Registration page in Filament 4?

All material that I've found is about Filament 3.

Thanks, Simon