Lithuanian main menu language on iOS (iPhone and iPad)

Dear fellows,

I am wondering for more than several years, is there any ETA when Apple will add a native LITHUANIAN language to its core iOS. I see really random countries and its languages, but not Lithuanian.

I have my parents using iPhone but with huge struggle, as they are forced to use Russian as their menu language, as they dont know any English nor any other language.

They love the devices, but they cant use them properly because Russian is not their mother tongue but only understand a little...

How hard is it to add a language...?! Please help me understand that.