Donkey milk represents a valuable alternative for diversifying dairy resources. The mixture of donkey milk with milk from other species may help overcome its technological limitations while creating opportunities for the development of innovative cheeses based on non-conventional milk sources and indigenous lactic acid cultures. The effects of adjunct Lacticaseibacillus and ripening time on the physicochemical, microbiological, proteolytic, volatile, and sensory characteristics of cheese were evaluated. Cheeses made from a mixture of sheep milk (70%) and donkey milk (30%) were manufactured using a commercial starter culture and served as the control. Experimental cheeses were produced from the same milk blend inoculated with the commercial starter culture and supplemented with autochthonous Lacticaseibacillus strains. Their addition accelerated acidification and modulated the volatile profile, increasing alcohol and ester concentrations while reducing aldehydes and branched-chain fatty acids. These changes may have contributed to enhanced aroma intensity and complexity, together with increased hardness and friability of the cheeses during sensory evaluation. The use of indigenous Lacticaseibacillus cultures may contribute to the production of innovative mixed-milk cheeses, supporting the sustainable valorisation of donkey milk in dairy systems.