fix: use an indepentant URL for checking internet connectivtiy

Author: DeepDiver1975

changelog/unreleased/41506

@@ -0,0 +1,8 @@
+Change: Use configurable URL for internet connectivity check
+
+Default URL is now configurable and the default is set to an independent
+resource: https://detectportal.firefox.com/success.txt
+This also provides an IPv6 compatible URL.
+
+https://github.com/owncloud/core/pull/41506
+https://github.com/owncloud/core/issues/41465

config/config.sample.php

@@ -758,6 +758,10 @@
  */
 'has_internet_connection' => true,
 
+/**
+ * The following URL is used to detect internet connectivity.
+ */
+'internet_connectivity_detect_url' => 'https://detectportal.firefox.com/success.txt',
 /**
  * Check for a `.well-known` setup
  * Allows ownCloud to verify a working .well-known URL redirect.

settings/Controller/CheckSetupController.php

@@ -83,9 +83,9 @@ private function isInternetConnectionWorking(): bool {
 		}
 
 		try {
+			$detectUrl = $this->config->getSystemValue('internet_connectivity_detect_url', 'https://detectportal.firefox.com/success.txt');
 			$client = $this->clientService->newClient();
-			$client->get('https://www.owncloud.com/');
-			$client->get('http://www.owncloud.com/');
+			$client->get($detectUrl);
 			return true;
 		} catch (\Exception $e) {
 			return false;