###Example using existing "Not Ubuntu" off-topic reason:

> Questions on **Linux or Unix** which don't involve Ubuntu are
> off-topic here, but can be asked on [Unix & Linux Stack Exchange][1].

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###Rewording to include official derivatives:

> Questions on **Linux or Unix** which don't involve Ubuntu or its [recognized flavors][2] are
> off-topic here, but can be asked on [Unix & Linux Stack Exchange][3].


  [1]: https://unix.stackexchange.com/about
  [2]: http://www.ubuntu.com/about/about-ubuntu/derivatives
  [3]: https://unix.stackexchange.com/about