https://www.theverge.com/2019/1/14/18182389/rocket-league-cross-play-enabled-ps4-switch-xbox-pc

Sony is enabling cross-play support for Rocket League today. This now allows PS4 Rocket League players to play against gamers on Xbox One, Nintendo’s Switch, or Steam PC players. Sony had previously limited Rocket League cross-play to just between PS4 and PC, and Rocket League developers Psyonix revealed it was waiting on Sony to stop blocking cross-play. Sony eventually backed down on both Fortnite and Rocket League cross-play with a new policy change last year.

The policy changed followed months of pressure on Sony from both fans of Fortnite and Rocket League to enable cross-play support in both titles. Rocket League developer Psyonix is enabling cross-play by default, and a future update will also allow players to party up across platforms. Players will be able to create private matches to specifically partner up with friends until the update, otherwise it’s random matchmaking across PS4, Xbox One, Nintendo Switch, and PC.