Tracking error for not (anymore) existing site

I get a tracking error for a site that no longer exists in the Matomo admin. The client has stopped maintaining their site and is now doing it themselves. Should I have removed the tracking code before? I forgot to do that. What can I do to fix this error?

If you’re unable to get the script removed, you’re only left with one option: block the library’s http calls at the server level when coming in with the unwanted referrer.

The clients connecting to the offending website will eventually get a 403 on the library endpoint and nothing happens anymore.

We have the same issue (for the same reason!).

Matomo should have an option for “ignoring” (at least disable notifications) tracking errors for some deleted ids.