(like LineageOS) developed by third-party communities rather than OPPO.
If you are searching for a way to force the OPPO F3 to run Android 8.0, 9.0, or higher in 2021/2022, be cautious: oppo f3 update 80 download 2021
Wait for the device to check for new versions. If one is found, tap . or higher in 2021/2022