the Germanic speaking regions of the HRE have always had multiple Germanic languages. You had Old and Middle variants of Saxon, Frisian, Dutch, Franconian, Bavarian, and Swabian, all of which were mostly derived from different West Germanic branches, the Saxons and the Frisians from Ingvaeonic, Dutch and Franconian from Istvaeonic, and Bavarian and Swabian from Irminonic. It was mostly the same situation culturally, as the Franks, Saxons, Frisians, and Bavarians were all distinct Germanic tribes. It wasn't really until the 19th century with German nationalism and universal education that there developed a sense of a unified German identity, language, and culture.