Add a condition plugin for domain name

THX,
Working well for me with just two small modifications:
validateConfigurationForm it's not called for me (why?) so I moved the code (Store the trimmed domains as an array) in submitConfigurationForm:

 public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
    // Store the trimmed domains as an array.
      $domains = explode(PHP_EOL, $form_state->getValue('domains'));
      $form_state->setValue('domains', array_filter(array_map('trim', $domains)));

    $this->configuration['domains'] = $form_state->getValue('domains');
    parent::submitConfigurationForm($form, $form_state);
  }

Changed in evaluate (mb_strtolower)

      $host = mb_strtolower($this->requestStack->getCurrentRequest()->getHost());
      return in_array($host, array_map('mb_strtolower', $domains));