I don't know too much about the Islamic and African world, though I wish I did. However, on the topic of Celts... they were all over Europe in various forms and sub-cultures... the Celitberian and Celtic-influence Lusitani in Iberia, the Caledonians, Iceni, Casse, Cautevellani, and Goidils in The British Isles and Ireland, the Gallic folk in France, the Belgae around the Rhine area... the countless Alpine tribes (not counting independent cultures like the Rhaetians), the Cisalpine Gauls, the eastern Boii, Scordisci, and Lugii, and the Galatians in Greece, Turkey, and Egypt.
The Celts outside of main Europe were there often due to migration and mercenary service. The Anatolian Galatians in Ankyra conquered a chunk of land and then often lent their services as mercenaries to the Greeks and Pontics. The Egyptian Celts were imported there to be mercenaries, given land and slaves and enticed to settle along the Nile, in return for military service. The Carthaginians used Celts as mercenaries as well... and while their favored troops were Iberians, Numidians, and Libyans... they probably had Celts in Carthage...
So the Celts have spread all over the place, and while I'm not educated enough to speak on the Flyssa authoritatively, I know that the Celtic influence
is possible geographically... but time-wise... it is not so clear
