So far, it is in beta testing, but everyone can try it.
Remote Play Together allows you to invite other users to the game with a local multiplayer, co-op or shared / split screen. Up to four people can play (and in ideal conditions even more). It is enough that the game was installed only at the host, the rest are connected to it through Remote Play.
In order to test the new feature, you must first switch to Steam Beta.
Then run the game with local multiplayer. Then you can invite friends to the list of Remote Play Together.
When everyone is connected, you can start playing.
AT Steam Blog it is noted that the gamepads of your comrades will behave as if they are connected directly to your computer. At the same time, only the game will be displayed on their screens, your desktop or any data will not be displayed.
Remote Play Together is supported on PC, Mac, and Linux.