The Simple Domain Sitemap configuration form cannot be accessed. Update the module and reinstall this module and simple_sitemap but it doesn't work. I didn't find the problem.
Problem
Symfony\Component\Routing\Exception\RouteNotFoundException: Route "simple_sitemap.sitemaps" does not exist. in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 206 of core\lib\Drupal\Core\Routing\RouteProvider.php).
Drupal\Core\Routing\UrlGenerator->getRoute('simple_sitemap.sitemaps') (Line: 270)
Drupal\Core\Routing\UrlGenerator->generateFromRoute('simple_sitemap.sitemaps', Array, Array, 1) (Line: 105)
Drupal\Core\Render\MetadataBubblingUrlGenerator->generateFromRoute('simple_sitemap.sitemaps', Array, Array, 1) (Line: 765)
Drupal\Core\Url->toString(1) (Line: 182)
Drupal\Core\Utility\LinkGenerator->generate('You can check existing sitemap variants of domains', Object) (Line: 64)
Drupal\Core\Utility\LinkGenerator->generateFromLink(Object) (Line: 164)
Drupal\Core\Link->toString() (Line: 107)
Drupal\domain_simple_sitemap\Form\DomainSimpleSitemapConfigForm->buildForm(Array, Object)
call_user_func_array(Array, Array) (Line: 536)
Drupal\Core\Form\FormBuilder->retrieveForm('domain_simple_sitemap_config_form', Object) (Line: 283)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 169)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 718)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)