Yes, Julian was a Thracian, which was within the bounds of Greece, especially during his time. Zeno of Citium the Phoenician was accepted even earlier. Quoting late authors like Libanios doesn’t help in a universal sense, because their (urban) world was already jumbled up by imperialism (beginning with the Hellenistic) and thus Hellenism lost its original cultural identity and developed a false transcendental one. Even though I am a Greek, I can easily blame the Greeks for their cultural imperialism in the Near East, the same region where Libanios came from—he must have felt inferior if he were not considered Greek, and therefore he went along with the imperialism as a coping mechanism. A similar thing happens with immigrants in America, like my parents, and even happened with me when I returned to America after living 10 years abroad. And a brief note once again: Don’t be quick to equate the Greek philosophical system’s universal cosmology to what other traditional and regionalized cultures do with their cosmologies/mythologies, because that will lead to the dismissing of the latter, since modern science agrees often with the former.