If I would like ask a question that applies to just the default flavor of Ubuntu specifically (not Xubuntu, Lubuntu, Ubuntu GNOME, etc.), how should I phrase and tag it?
If it's specific to standard Ubuntu's DE (Desktop Environment) Unity, use the tag unity. Other flavours use other DEs (Xubuntu=XFCE; Lubuntu=LXDE; Kubuntu=KDE;...)
Additionally, you can clearly write in your question, that you want answers about standard Ubuntu with Unity and nothing that is different in other flavours. So simple is it. :)