Oembed broken for multi-language sites

Hmm, that MR seems to make an assumption, that there is a path prefix with the langcode. I think, that's not always the case. And there are probably even more ways to alter the routing.

Isn't it possible to use the Url service from Drupal to receive the correct path?

I used with and without prefix. But you are right: checking the route is the better solution. Commit added.

depending on how content/interface language detection is configured and whether content is translated in the detected language
the check by langcode might be unsuccessful.
checking if the initial_path ends with '/media/oembed' seems more reliable:

diff --git a/src/Utility/KlaroHelper.php b/src/Utility/KlaroHelper.php
index ef408e3..14e4f03 100644
--- a/src/Utility/KlaroHelper.php
+++ b/src/Utility/KlaroHelper.php
@@ -811,8 +811,6 @@ class KlaroHelper {
       }
     }
 
-    $langcode = $this->languageManager->getCurrentLanguage()->getId();
-
     foreach ($dom->getElementsByTagName('iframe') as $iframe) {
       if ($iframe->hasAttribute('data-src') && $iframe->hasAttribute('data-name')) {
         continue;
@@ -821,7 +819,7 @@ class KlaroHelper {
       $initial_path = parse_url($initial_src, PHP_URL_PATH);
 
       // If remote-video matchKlaroApp against url parameter.
-      if ((strpos($initial_path, '/media/oembed') === 0) || (strpos($initial_path, '/' . $langcode . '/media/oembed') === 0)) {
+      if (str_ends_with($initial_path, '/media/oembed')) {
         parse_str(parse_url($initial_src, PHP_URL_QUERY), $params);
         $found_klaro_app = $this->matchKlaroApp($params['url']);
       }

Thank you, @van.dordafog
I changed the code and updated the MR.

Thank you all for testing and feedback. I merge this and will tag a new RC.

Automatically closed - issue fixed for 2 weeks with no activity.