Psyonix has announced that it is withdrawing support for Rocket League on Linux and macOS as part of its push to update the game with "new technologies." In a statement, the company said that it was "no longer viable" to maintain support for the macOS and Linux / SteamOS versions of the title. Consequently, after a final patch in March, online functionality (one of the main reasons to play the game) will be deactivated.
After the update, online multiplayer and access to the store will be blocked, although local multiplayer and split screen will still work. You'll also be able to see your existing garage and inventory, and your career stats won't be lost. Psyonix has said that affected users will be able to download the Windows version of the game in compensation, should you have the rig to play it on.