What is the link to the closed wiki, and when it was closed? In most cases, there is a time that you can download a copy directly from the "Wiki was closed" page.
The full-history dump is not available but the current-version dump generated around 2020-10-02T15:21:00Z can still be downloaded directly. In that dump, the last edit was made at 2020-10-02T10:34:31Z.