Survey Data on European Organic Multi-Species Livestock Farms - Ulukan, Defne; Steinmetz, Lucille; Moerman, Marie; Bernes, Gun; Blanc, Mathilde; Brock, Christopher; Destruel, Marie; Dumont, Bertrand; Lang, Elise; Meischner, Tabea; Moraine, Marc; Oehen, Bernadette; et al. (Frontiers in Sustainable Food Systems, 2021)