@F1nansist I got an international version working!
Digging through the various files and documentations I stumbled upon FTextTransformer
You just need add
#include "Internationalization/TextTransformer.h"
Then you can try
FString s(TCHAR_TO_UTF16(*passedText));
FString passedTextLow = FTextTransformer::ToLower(s);
FString passedTextUP = FTextTransformer::ToUpper(s);
Where passedText is a FString
Seems to work with many other languages. I tested it with Polish and it does upper case and lower case well, also did a quick test with some Russian letters and seems to handle them well 
@EpicChris I was wondering if someone from the staff could maybe incorporate a comparison like this natively for unicode test of the contains function for strings?
Native uppercase & lowercase for FText should use UTF16 with FTextTransformer or at least have an option for unicode compliant conversion? (maybe a bool)