Symfony\Component\Routing\Exception\MissingMandatoryParametersException: Some mandatory parameters are missing ("openid_connect_client") to generate a URL for route "openid_connect.redirect_controller_redirect".

@akshaykamble
If you are building the URL and migrating from 1.x to 3.x, you need to see your code.

$redirect_uri = Url::fromRoute(
          'openid_connect.redirect_controller_redirect',
          [
            'openid_connect_client' => $openid_connect_client,
          ],
          [
            'absolute' => TRUE,
            'language' => $language_none,
          ]
        )->toString(TRUE);

Change "client_name" to "openid_connect_client". The entity name has changed.

Think this is a support request and not a bug? Await feedback from @akshaykamble