I saw this question, GTK disappears while in sudo mode, which appeared to be about a derivative Ubuntu release.
Do we support derivatives of Ubuntu? Or have I misidentified the question?
It's funny the difference a week makes.
Ubuntu MATE is official now; it is supported on Ask Ubuntu.
Standard rules apply though so bugs and major pre-release issues should primarily be reported through the bug tracking tools on Launchpad.
I think that is in the air right now, as they are on the way to be official and they have number releases corresponding with Ubuntu and still have "Ubuntu" in the title, as it seems the legal team is diligent in having derivatives remove that.
Since their goal is close compatibility, aka as pure as possible Ubuntu + Mate for the desktop - which can be added via ppa as well, it would be reasonable to let some through, till it's official.
However some still apply rules hard and fast without grey areas, and will still close until the day that happens.
This however isn't on the scale of mint, so I wouldn't be so fast to burn these questions.
In relation to that specific topic: closing something as a duplicate is better than closing something as off topic even when the question is related to an unofficial release. We are a friendly bunch though sometimes some of us can not prevent being firm or even (a bit) harsh but the 1st does an attempt to help the user and the 2nd just cuts of the user.