OnePlus is one of the few Android manufacturers that rolled out the Android 10 update only a few days after Google. While OnePlus 7T series of smartphones run Android 10 out of the box, relatively old OnePlus 7 series is currently receiving the update. OnePlus 6 and 6T, OnePlus 5 and 5T will get the Android 10 update too.
Unfortunately for OnePlus 3 and 3T users, the company did not include the OnePlus 3 series in the list of smartphones that will be getting the Android 10 update. In other words, OnePlus has no plans to roll out the Android 10 update to OnePlus 3 series of smartphones.
However, that doesn’t mean that you cannot get the taste of Android 10 on your OnePlus 3/3T. Unlocking the bootloader, which in turn, would require your handset to be running OxygenOS 9.02 firmware or newer and TWRP 3.3 or newer, would be the first step. You will then need to download and install TWRP recovery on your OnePlus 3 or 3T.
You can now download any of the Android 10-based custom ROMs on your smartphone from the above link. The final step is to boot into TWRP recovery. You can also check out this post from OnePlus that will help you out with the process of Unlocking the Bootloader and flashing TWRP.
Before you proceed, make sure to take the backup your data and don’t forget to keep battery percentage over 60.
Since you’re installing an unofficial build of Android 10, MSPU is not liable for any damaged caused to your OnePlus 3/3T. Perform it at your own risk!