[hadiz]

Well, you just kinda answered your question. There is STL, Qt and Boost. Like all other languages. They do the same thing but in different capacities, you should select based on your needs. I think std::string can be supplemented for Unicode support, I am gonna say the fmt library was the supplement but I feel like I am wrong.

I used std::string and QString extensively for 4-5 years and find QString inexplicably bloated and un-intuitive for my use cases.

[ahartmetz]

I don't understand your problem with QString, but anyway, AFAIK the common way to get Unicode support with std::string is ICU. ICU is quite large (~15-20 MB binary) and it breaks binary compatibility with every release.

[hadiz]

I don't do C++ anymore professionally, but from I remember, std::locale was very useful: https://en.cppreference.com/w/cpp/locale

And QString had no magic to it other than wrapping its underlying data in ytf-16 which std::u16string does too.

It's not perfect but it gets the job done, IIRC.