You can find community-maintained versions of or AOSP-based ROMs on forums like XDA Developers . Note that these are "Stock Android" experiences and will not feature the ColorOS interface you may be used to. Risks and Warnings
Because Oppo prioritized the "Selfie Expert" experience over long-term OS upgrades for this specific model, the only way to run Android 8.0 is through unofficial custom ROMs. The Reality of Official Updates oppo f3 android 8 update download
The Oppo F3 originally shipped with and ColorOS 3 . While some regions received a beta update or official migration to Android 7.1 Nougat , the manufacturer never rolled out an official migration to Android 8 Oreo. Last Official Version: Android 7.1 Nougat (ColorOS 3.1). You can find community-maintained versions of or AOSP-based
The situation was further complicated by Oppo’s software strategy at the time. The company was transitioning from ColorOS 3.0 to ColorOS 5.0 (which was based on Android 8.1). In many regions, Oppo seemingly skipped the Android 7.0 Nougat iteration entirely for the F3, attempting to jump straight to Oreo. However, the implementation was spotty. Many users who successfully updated found that while the Android version number changed, the user interface remained heavily locked down. The much-vaunted "Project Treble" benefits were often neutered by Oppo's proprietary modifications, meaning the update did little to solve the underlying fragmentation issues. The Reality of Official Updates The Oppo F3
If you are determined to run Android 8.0 or higher, you must use Custom ROMs . This process is risky and intended for advanced users: OPPO Software Update : Step-by Step Guide