https://wccftech.com/red-dead-redemption-2-gets-steam-page-ahead-of-december-5th-launch/

Red Dead Redemption 2 launched earlier this month on PC, though it's not yet on the most popular digital storefront, Steam.

That will change very soon as the game's page is now up on Valve's store. Red Dead Redemption 2 will be available there on December 5th. Do note that the Rockstar Games Launcher is still required even if you purchase the game from Steam.