I suppose nationalism would become a major factor in the Byzantine Empire, like it did in the Ottoman Empire in reality.
I'm not sure how accurate this map is for the area in question, but I post a fragment of a map "Languages of Europe by the end of the 15th century".
So it shows linguistic situation in former Byzantine areas around the time of the Fall of Constantinople (most of Anatolia is already Turkish-speaking).
Bronze color = territory with majority of Greeks / Greek-speakers - Greek was spoken mostly along the coasts as it seems:
Legend:
I'm not sure how accurate this map is for Albanians. Serbian historians say, that Albanisation of Kosovo started only during the 1690s.
And this map seems to suggest, that Kosovo was already mostly Albanian-speaking by the end of the 1400s.
So pay attention to the fact that this map may be inaccurate in some areas - if you think you know what is wrong in it, you can tell me.