Assuming you have unlocked bootloader and downloaded your chosen ROM ( .zip ) + GApps (NikGapps recommended).
Development for Oppo’s A-series is nearly dead because: Oppo A9 Custom Rom
Oppo A9 2020 (CPH1937/CPH1938) is a challenging device for custom ROM development due to Oppo's historically restrictive bootloader policies and the device's age. While the hardware remains capable in 2026, official software support ended years ago, making custom ROMs or Generic System Images (GSIs) the primary way to access newer Android versions like Android 14 or 15. 1. Preparation and Prerequisites Assuming you have unlocked bootloader and downloaded your
: Unofficial ROMs for this device often suffer from bugs in critical hardware components, such as the camera or fingerprint sensor. Proceed at your own risk
on your phone and may void your warranty. Proceed at your own risk. Phase 1: Prerequisites Backup Everything