How to redirect from a Form using setRedirectUrl() method in Drupal

customForm.php

<?php

In the submitForm() method of your form class, create a new instance of the RedirectResponse class, which is used to redirect to a new URL.

// Use the setRedirectUrl() method to set the URL to which you want to redirect. You can pass the URL as a string or as an instance of the Url class.
// Return the RedirectResponse object from the submitForm() method to trigger the redirect.
// Here's an example of how to use setRedirectUrl() in a form class:

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Routing\RedirectDestinationInterface;
use Drupal\Core\Url;
use Drupal\Core\Form\FormBase;
use Symfony\Component\HttpFoundation\RedirectResponse;

class MyForm extends FormBase {

  public function getFormId() {
    return 'my_form';
  }

  public function buildForm(array $form, FormStateInterface $form_state) {
    // Build your form elements here.
    return $form;
  }

  public function submitForm(array &$form, FormStateInterface $form_state) {
    // Get the URL to which you want to redirect.
    $url = Url::fromRoute('my_route');

    // Create a new RedirectResponse object.
    $response = new RedirectResponse($url->toString());

    // Set the redirect destination.
    $response->setRedirectDestination(
      \Drupal::service('redirect.destination')->get()
    );

    // Set the redirect URL using setRedirectUrl().
    $response->setRedirectUrl($url);

    // Return the RedirectResponse object.
    return $response;
  }
}