Context
In the undermentioned, there is discussion amongst KDE developers and users about why their relevant regional format configuratior does not support choosing arbitrary formats, even predefined ones, for all except one type of regional format:
The conclusion has been that this is due to GlibC’s locale implementation, which itself adheres to the POSIX specification: [1]
The way localization works on POSIX systems is through locales. There simply is no concept of standalone date or time format. [2]
However, as others have correctly explained, lower-level standards can be augmented by more granular, higher-level ones: [3]
There is nothing requiring KDE applications to use the POSIX locale infrastructure itself. In fact, as you surely know, they actually don’t behind the scenes: QLocale internally translates the POSIX locales to ICU locales and uses the ICU infrastructure (which is unfortunately not any better, and the translation also means custom glibc locales, or even the glibc en_DK locale, do not work in Qt applications). Up to KDE 4, they used KLocale which bypassed the POSIX locale infrastructure entirely.
Question
I am writing gitlab.com/-/snippets/4823517, which details the differences in regional adjustment support between Windows ≥ 11 (which handidly beats all competitors), AOSP ≥ 14, KDE Plasma ≥ 6.3, and, hopefully, macOS and GNOME ≥ 42.
However, unlike the rest of the aforementioned (except macOS), I’m rather unfamiliar, nowadays, with how GNOME and GTK do most things.
Consequently, is it currently possible (presumably in gsettings) to explicitly choose, for instance, ISO 8601 or RFC 3339 for timestamps, in the stead of choosing a locale which merely happens to adhere to that standard? If not, can I at least, like macOS and AOSP, choose Celsius or Farenheit for temperatures, irrespective of locale?