I solved this using something like that:
import i18n from "i18next";
import detector from "i18next-browser-languagedetector";
import Backend from "i18next-xhr-backend";
import { initReactI18next } from "react-i18next";
i18n
.use(Backend)
.use(detector)
.use(initReactI18next)
.init({
lng: 'it',
supportedLngs: ["it", "en"],
backend: {
loadPath: "/locales/{{lng}}/{{ns}}.json",
},
ns: ["common"],
defaultNS: "common",
fallbackLng: [ "it", "en"],
});
export default i18n;
lng:'it' is the relevant part