I just noticed that the ‘Free Culture’ category is not visible on the main forum site. See: https://ubuntu-mate.community/
Perhaps this is a reason why it is not frequented so often?
It’s intentional that they’re hidden. They’ve been always empty even when they were around last year.
When the categories were first re-organised, I suggested their removal but @Wimpy said to keep them so that he can kick start “Free Culture” again at some point.