OxygenOS 5.0.7 update is based on Android 8.0 Oreo. As announced earlier, OnePlus won’t upgrade OnePlus 3 and OnePlus 3T to Android 8.1 Oreo, instead both devices will get the latest Android 9 Pie update. The Pie update will be available on the OnePlus 6/6T, OnePlus 5/5T and OnePlus 3/3T, in that order.
OxygenOS 5.0.7 OTA is live now. Since the roll out is in phases, it will take a few days to reach on all devices. To get now, use a VPN (like Tunnelbear) and set the location to Germany or Canada. You can also download and install the OxygenOS 5.0.7 stable update manually, if you wish so. Please back up your data before flashing the update manually your device.
How to Unbrick a Bricked (Non-Booting) OnePlus 3T
Installation Guide
Download the firmware zip file from OnePlus download section [HERE] and save the zip file on your phone’s storage. Now, go to ‘Settings’ – ‘system update’, tap the ‘settings’ icon on the top right corner, choose ‘Local upgrade’, find the .zip file and tap on ‘Install’ to confirm. The update takes about a minute (depending upon the file size), once done reboot your device to boot into the latest Oxygen OS. If you have replaced the stock recovery with TWRP, then to install this update, boot your phone into TWRP, select “Install” > select the ROM zip file > swipe to flash and then reboot your device. If you are on a custom ROM, then a clean flash is necessary. (source)
