Ubuntu "flavors" (*buntu in the name) all use the same package pool directly, and users sophisticated enough to post a bug report are generally aware they're using an Ubuntu version. I support all of them.
Ubuntu derivatives (such as mint and elementary os) might use binary copies of the packages, might do rebuilds, and might replace certain packages. They should be listed as either "other" or their own category if they're popular enough for bugzilla purposes (mint in particular). I don't support them.