Anatolia was home to the “Ancient Anatolians,” an Indo-European people (Hittites, Luwians, Lycians, Lydians, etc.). The Aegean, Mediterranean, and Pontic coasts of Anatolia had been seeing Greek colonization since the 8-6th centuries BC. East of the Euphrates is the Armenian Highlands (the western portion is referred to as “eastern Anatolia” by the Turks since the 1920s | the eastern portion is referred to as “the lesser Caucasus” by the Russians since the 1920s). In the 4th century BC Alexander the Great conquered the region and Hellenization became more intense.

There were some other people’s in the area, such as the Phrygians (an Indo-European people originally from Thrace) who migrated into Anatolia and toppled the Hittite empire around 1200 BC and settled in central Anatolia. In the 3rd century BC a Celtic group from the Balkans, the Galatians, migrated to the same area as the Phrygians and settled among them in Central Anatolia.

So the native Anatolian languages (6th century AD), Phrygian (5th century AD) and Galatian (4th century AD) had all been replaced by Greek way before the Seljuk Turks came in the 11th century.

When the Seljuks came, the western parts of Turkey were Greek-speaking, the central parts were mostly Greek with a large Armenian presence, and the east was Armenian-speaking. The southeast had Arabic, Aramaic (Assyrian) and Kurdish presences and the northeast had Kartvelian (Georgian and Laz presence).

While Armenian, Greek, and Aramaic have been largely wiped out of modern-day Turkey during the Genocides of WWI (expect for some 60,000 Armenians, 20,000 Syriacs and 2,000 Greeks in Istanbul), the Muslim non-Turks such as the Kurds, Zazas, Laz and Arabs survive. There are also 5,000 Aramaic-speaking Christians, largely Syriac Orthodox remaining in the southeast, near Mardin, in an area called Tur Abdin (mountain of servants; the historic monastic homeland of the West Syriac Rite).

Hope that answers your question! Feel free to ask if you have any further!