Have there ever been any Protestant reformist movements that grew from within Orthodox countries? By this I mean movements that were not the result of missionaries from former Catholic countries, but movements having a more East European/homegrown origin.
Russia has had plenty. The Doukhobory were one, the Molokane another, and while not much is known about them, the Judaizers of the 15th Century might count, although from what little we know about them, it is speculated that their movement might have come from Protestant ideas spreading east, from Germany, to the Polish Lithuanian Commonwealth, into Ukraine and Muscovy.
I also wouldn't look to the Old Believers or the Old Calendarists of Greece: these were movements that believe the same dogma and adhere to the same ancient rituals as the Church as a whole, but believe that the Church is going about it the entirely wrong way and that it has lost its mission. If you asked any of them about Sola Scriptura, neither of these groups would be too pleased.