Using casefold did not help

ubuntu Lang is en_US.UTF-8
[GCC 9.3.0] on linux
>>> folded_1: str = "Turkish I: İı".casefold()
>>> folded_2: str = "tUrkİsh i: iI".casefold()
>>> print(folded_1)
turkish i: i̇ı
>>> print(folded_2)
turki̇sh i: ii
>>> print(folded_1==folded_2)
False

It exhibits the same shortcoming as toLower.
multi-language support ain't easy, especially when everything you learned about strings ain't true.