Since the official mobile version is still in development, these free alternatives offer similar "bullet-hell" or high-intensity rhythmic gameplay: Beat Saber

Since there isn't a direct "Install" button yet, players use these workarounds: Winlator / PC Emulation:

If you own the PC version of Project Arrhythmia, there is a safer way to play it on your Android device without resorting to shady APK sites: