OxygenOS Open Beta 1 should be first installed manually on OnePlus 6T. The subsequent updates will roll out via OTA (over the air). The first beta build includes December 2018 security patch, lets you migrate data from iPhone, show call history for incoming calls from unknown numbers and more. Recently, OnePlus released OxygenOS Open Beta 9 for OnePlus 6 with similar features.

OxygenOS Open Beta 1 changelog: OxygenOS Open Beta builds are almost stable, so it can be used as a daily driver. However, there might have some unknown bugs that may affect performance of the device. If you are interested, here is how to install the beta build manually on OnePlus 6T.

How to Install OxygenOS Open Beta 1 one OnePlus 6T

  1. Download the OxygenOS Open Beta 1 ROM zip file from this link and transfer it your OnePlus 6T’s storage.
  2. Open the ‘Settings’ app on the phone, then go to ‘System updates’, and then tap on the top right corner icon.
  3. In the menu, tap on Local upgrade, then choose the upgrade package and then immediately upgrade.
  4. System will start the upgrade process. Once done, select Reboot system now. Your OnePlus 6T will reboot into new OS. (Source)