Your Data is Valuable

Please make sure you had your data backup.

There is a built in backup app in OnePlus phone, see the official guide about how to backup your data.

How to install HydrogenOS 11 Developer Preview on OnePlus 8 Series

Full guide from xda-developers

How to install OxygenOS 11 Developer Preview on OnePlus 8 Series

Full guide from StopToExplore