Some games will refuse to start if you rename their. To make multiple games work this way, either temporary rename the game A's folder, repeat the above steps and switch between folders when necessary, or use other steam titles you own instead Send your friend a remote play together invite through steam overlay or friends list window.

If the game doesn't start (steam_api.dll errors and the like) try a scene release or the GOG version in step 2. Rename the game B's executable so it has the game A's original name (Cuphead.exe to Jamestown.exe), also rename Cuphead_Data folder to Jamestown_Data (required for all Unity engine games i believe). Rename the game A's executable or delete it if you wish. Unzip the contents of the CSF package to the game A's location, pay attention to the folder and file structure, DO NOT overwrite or edit original steam_appid.txt and steam_api.dll files.

Go on the interwebs, find and download clean steam files for the game of your choosing (let's call it game 'B', Cuphead in my case).

I used Jamestown (no particular reason other than it being a small one). Install a remote play together ready game through steam (let's call it game 'A'). Hello, this is my first post on reddit and it's about my experience with recently made available Remote Play Together steam feature.

Steam unlocked cuphead