As his name – and the fact that he gets a Wikipedia entry only in German – doesn’t indicate, Stuppner is Italian. It is true that he comes from South Tyrol, the region still today very disputed with Austria, where over 60% of the population speaks German.
Anyway, Stuppner has only a very limited presence in my collection and reviews, through a folksong arrangement, O moj babo, sultan sulejmane, performed by Johanna Knauf and Ensemble Musica ‘900 under Maurizio Dini Ciacci on a collection in homage to Berio, Folk Songs (with works of Betty Olivero, Andrea Mascagni, Carlo Galante, Zygmunt Krauze, Virgilio Savona, Salvatore Sciarrino, Claudio Ambrosini, Andrej Petrov, Luca Francesconi, Walter Zimmermann), Dischi Ricordi CRMCD 1009 (1989)