I had a similar problem but my operating system language was English. After reading this answer, I changed my operating system language to Turkish and also changed my Region and other related settings to Turkey, then I got the Turkish characters. And I tried your code that you can see below.
figure
xlabel('ğ')
ylabel('ç')
title('ö ç ş ğ ü')
>> feature('DefaultCharacterSet')
ans =
'windows-1254'
Result is:
