Unix is very much on topic here and always has been. Yes, we get fewer questions about Unix than we do about Linux, but we certainly get questions about both. We also get questions about macOS and Cygwin, both of which are on topic here.
As an aside, tags are not the primary way of indicating what OS a question is about, that is often found in the body of ...
For something like:
interesting questions were asked say within the last week or two and if votes were 5 or more.
.. I would use these search criteria:
Is:q score:5.. created:14d..
it's a question
is scored 5 or higher
was created less than 15 days ago
I often refer to the search help page that's linked from the advanced search tips within the ...