Are locales supported?
Test for Serbian, Bosnian, Belorussian, Hawaiian, and Norwegian Sami. Bear in mind if the base local is supported, it will report it as supported.
JavaScript
console.log(Intl.DateTimeFormat.supportedLocalesOf(["en-GB", "en-AU", "en-CA", "en-IN", "de-CH", "de-AT", "fr-CA"]));