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spanaa nos aporta un .zip flasheable por recovery:
https://www.androidfilehost.com/?fid=24459283995303758
Changes firmware from Hydrogen OS 6.0.1 to Oxygen 2.2.1 and replaces TWRP with twrp-2.8.7.0-oneplus2. After flashing this zip, reboot recovery and restore your full Oxygen 2.2.1 nandroid backup or flash the full Oxygen 2.2.1 zip