How to report a problem with Google Talk to Google?

Recently[1] DuckDuckGo updated their XMPP server (Prosody) to the new version which makes server to server encryption mandatory. This broke federation with the Google Talk service, essentially cutting off all users who were communicating between these two services before. While the move to mandatory encryption is reasonable in this day and age, if Google won't fix that on their end, many would lose communication with majority of their contact lists.

Is there any way to report this bug to Google? Since Google focuses on walled garden / non federated Hangouts now, they don't make it easy to report anything about Google Talk to them. On the other hand they still run the service, so some maintenance should be normal to expect. Any advice how to reach Google with this problem?

Thanks.

[1]: https://duck.co/blog/xmpp-s2s