Everyone has at least one friend without a Steam account, who isn’t going to get one just so you can play Cuphead together, because signing up for a new platform means making yet another password and it’s just a WHOLE THING that your friendship really isn’t worth.
Well, now you can play with them on Steam without any commitment to new login details, as long as your game supports Remote Play Together and you can convince them to download Steam.
The latest Steam update included adding the friendly new Invite Anyone feature to the already existing Remote Play Together functionality. Just launch one of the thousands of games that support Remote Play Together, like Overcooked!, Stardew Valley, Left 4 Dead 2, or Divinity Original Sin 2, copy the invite link from your Friends list, and send it to anyone you want, they just have to have the Steam client installed (not an actual account). It works on Windows, Linux, macOS, Android, and iOS, and you don’t have to download or install the actual game since it’s streamed. For best results you’ll need a 10 to 30 Mbps connection.
Remote Play Together has been a feature of Steam since 2019, but it was only for people with Steam accounts. Now it’s for EVERYONE.