Supongo que esto sería interesante añadirlo al primer post:
Reverts firmware from Hydrogen OS 6.0.1 back to Oxygen 2.2.0 and replaces TWRP with twrp-2.8.7.0-oneplus2. After flashing this zip, reboot recovery and restore your full Oxygen 2.2.0 nandroid backup.
https://www.androidfilehost.com/?fid=24399994186369132