Rockstar announced via Twitter that Red Dead Redemption 2 will be coming to Steam on December 5th. RDR2 is currently only available on PC through the Epic Games store.
Here is the Twitter announcement:
Red Dead Redemption is an action-adventure game developed and published by Rockstar Games. It was released for the PlayStation 4 and Xbox One in October 2018, and for Microsoft Windows in November 2019. The game is the third entry in the Red Dead series and is a prequel to the 2010 game Red Dead Redemption. The story is set in 1899 in a fictionalized representation of the Western, Midwestern and Southern United States and follows outlaw Arthur Morgan, a member of the Van der Linde gang. Arthur must deal with the decline of the Wild West whilst attempting to survive against government forces, rival gangs, and other adversaries. The story also follows fellow gang member John Marston, the protagonist of Red Dead Redemption.