Can I still claim Rocket League on Steam?

With the Free-to-play update, Rocket League has become available for download through the Epic Games Store and was delisted from Steam: https://www.rocketleague.com/news/patch-notes--free-to-play-release/ (Opens in a new tab)

Rocket League is only available for players who owned Rocket League on Steam before it went free-to-play. Epic Games Support cannot grant Rocket League on Steam.