Not yet. Do you have some Posix document, RFC, best practice guideline, etc showing that it should be "C.UTF-8" instead of "UTF-8"? Something to present to Apple proving that they are not Posix compliant?
https://pubs.opengroup.org/onlinepubs/9699919799/functions/setlocale.html says "The contents of this string are implementation-defined." I could live with having to run localedef once to define a locale UTF-8 at installation time, but that is wiped out again and again, see #965323. What would you suggest? Regards Harri