What's the difference between Super User, Unix and Linux, and Ask Ubuntu? In general, what's a rule for deciding where to post a question when I have one (which might apply to any of those 3)? If I'm having a problem with Linux Mint, which seems likely to be the same in Ubuntu, is it appropriate to post it on Ask Ubuntu?
Ask Ubuntu is for (from their FAQ):
Also from their FAQ:
In general, AU is for Ubuntu, Lubuntu, Kubuntu, Xubuntu...etcetera, while U&L is open to all other distros (while Ubuntu is acceptable there, if you only care about Ubuntu, you'll get more focused answers on AU).
In your case, I would ask on Unix & Linux.
Super User concerns itself with computer hardware, software, and personal home computing/networking; Unix and Linux concerns itself with *nix operating systems (not specifically a particular distro); and Ask Ubuntu concerns itself with questions in regards to Ubuntu and its official derivatives.
To answer your question more pointedly:
...so you'd do well with Unix and Linux.