Yes, there is Crossplay in Among Us. You can play with other players even if they play on other platforms. Crossplay is available for all platforms on which the game was released, namely PC, iOS and Android.
To connect to the game, choose the Online option. It allows you to join open rooms and play with random people, but if you want to play with your friends, choose the Local option. After selecting this option, create a server according to your preferences and then give the code to your friends so they can join your server.