Pre-registration for the global client of NieR Reincarnation is currently available on Android and iOS devices. Twitter user RedMakuzawa shared a screenshot, showing that pre-registration for the app outside of Japan is now open. This includes North America. [Thanks, RedMakuzawa!]
However, while pre-registration for NieR Reincarnation is currently available for Android and iOS devices worldwide, there is currently no confirmed release date for the global version of the title. In May 2021, Director Daichi Matsukawa released an official statement through the NieR Reincarnation Twitter stating that the English localization for the game was completed. That said, as it stands, the NieR Reincarnation Twitter account has not provided any update regarding a potential release date.
The Japanese client of the game has seen several collaborations with other NieR related titles. This included a NieR: Automata collaboration event which added 2B, 9S, and A2 to the game. The most recent collaboration saw Zero from Drakengard 3 added to the roster through a limited time event. Additionally, NieR Reincarnation featured a NieR Replicant collaboration leading up to the release of the remaster.
NieR Reincarnation is available now on Android and iOS devices in Japan. A global version is currently in development. However, a release date for the global client has yet to be announced.