Direct-to-Device (D2D) is clearly emerging as a key driver in the transformation of the satellite segment, in both of its main approaches. On one side are the established Mobile Satellite Service (MSS) operators, aiming to expand their offerings by adopting new 5G NTN (Non-Terrestrial Networks) standards for next-generation mobile devices. On the other side are new entrants, such as Starlink and AST SpaceMobile, deploying large LEO constellations and seeking to reuse terrestrial mobile spectrum, targeting customers with existing devices, without requiring modifications or upgrades.