Cross-play is fully supported.
MOD maps will support cross-play by the end of the year. At that time, the Steam Workshop will be deprecated and replaced with a new MOD system. This upgraded system will offer a smoother, more secure gameplay experience than what is currently available.
Posted by the game’s developer or publisher to its Steam community hub and published by Valve through Steam’s public news API. Sifter reproduces it unedited and writes none of it.