Understanding thermal transport in materials is one of the major challenges today, fundamental for engineering new materials efficient for thermal management and energy harvesting. A good understanding of heat transport mechanisms is now achieved for crystals on one side and disordered materials (glasses) on the other, which exhibit very different properties. A new class of crystalline materials, High Entropy Alloys, characterized by a strong local chemical disorder, exhibits thermal transport properties similar to the ones of glasses: understanding the origin of this behavior requires investigating their phonon dynamics.