We’re looking at the Storm-Eater customization option for the Renewed Proto-Drake coming in Dragonflight.
The Gladiator mount in Dragonflight Season 1 is an actual Dragonriding mount which makes me believe it will work the same way for the Mythic Raszageth mount.
Blizzard also added Renewed Proto-Drake: Embodiment of the Storm-Eater, a new type of item called Drakewatcher Manuscript that unlocks the new customization option for the Renewed Proto-Drake.
The mount is a customization option tied to the Renewed Proto-Drake and cannot be customized.