Some regions saw a limited beta for Android 7.1.1 Nougat (ColorOS 3.1), but it was never widely rolled out as a final stable build for all global variants.

Since this requires wiping your data, use the Oppo Clone Phone or a PC backup tool first. Where to Find Downloads

The device will automatically check the Oppo Update Servers for any available OTA (Over-The-Air) packages. If an update is found, tap . Running Android 8.0 via Custom ROMs

You will need to flash a tool like TWRP (Team Win Recovery Project).

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