Even for OnePlus it begins to become difficult to manage all its devices, therefore as happened with other rival brands the word End to the Oper Beta program relating to OxygenOS for OnePlus 6 and 6T is put. The announcement is made by the company via the official forum thus explaining also roll back to the stable version of the UI.
The reason for this choice certainly lies in wanting to guarantee the smooth running of the Beta program and to introduce new devices. So the owners of OnePlus 6 and 6T will and will have to return to the stable version OxygenOS 10.3.2 via rollback, considering that the updates will continue to arrive but only in a stable format. Finally, it should be noted that the transition from beta to stable via rollback will delete all the data of the device, therefore it is recommended to make a backup of your most important data.
OxygenOS Open Beta ends for OnePlus 6 and 6T: here's how to roll back
IMPORTANT: The procedure described in this guide presents complex operations which, if performed incorrectly, could damage your device. It is recommended to run it only by users who have gained a good experience in modding. For more details on the procedure, please refer to thread on the official OnePlus forum.
Having made the necessary recommendations, therefore, to proceed with the rollback procedure you must download the package dedicated to your device OnePlus 6 or OnePlus 6T. From the File Manager of your smartphone move the package you just downloaded from the Downloads folder to the main directory.
Now get in Settings, System, System Updates, press the button at the top right and choose the option to Update via local file. Now select the downloaded package and start the procedure.