Hey,
You may not want to check for “last updated” but “last contact” instead. This will not change until further communication articles have been created. I think that would be what you’d need.
Keep in mind, especially for last contact, that Zammad has two modes in updating this value. You can find more information on that (and the reasons) here:
https://admin-docs.zammad.org/en/latest/settings/ticket.html
(see ticket last contact behaviour)
Sorry, but this is not possible I’m afraid. This would help only a small percentage of Zammads user base. If you require german support, we can offer a support contract if required.