Problems that do absolutely exist on linux systems. I'm not talking about the poor choice of Windows using wchar_t for their native interfaces.
I'm talking about problems like char doesn't have a signedness defined, and that you can change it to be signed or unsigned with a compiler setting, a problem that makes checks like " val < 'A' " ill-formed.
This isn't the case with char8_t, char8_t is unsigned. " val < u8'A' " is well-formed.