As the name suggests, Steam Remote Play Together allows you to play local multiplayer games across a variety of devices. Valve advertised the feature as only available for Windows, Mac, and Linux, but it looks like it also works for Android and iOS. According to a report by The Verge, Steam Remote Play Together runs on Android and iOS. The outlet said the following.
Today, Remote Play Together is officially available for everyone, with what could be a really cool new feature — you can play with your friends using iOS and Android devices as well. According to Valve, the host player just needs to install and start the game, and friends on PC can join in via Steam Remote Play or on mobile with the Steam Chat and Steam Link apps. Only the host needs to actually own the game, which is nice.