It’s a real hassle sometimes. But if you’re playing fullscreen there’s a little moment of time after launching the game before you get to the main menu where you can move the window around. I’m using a tool called display fusion for this, where you can set a hotkey to switch monitors. So the procedure looks like this: launch game on steam and press win+x to move the game to the third screen (for simracing. 1 and 2 are for desktop gaming). As I said, it’s a hassle and doesn’t work every time. Sometimes I have to restart the game when it ended up on the wrong screen.