The release referred to is the Open Beta 4 of Android 10 and although there is not yet a thread on the official forum, OnePlus has made available for downloading the OTA files to download and flash.
The innovations introduced within this build are different: among these, an improvement in system stability, the Android security patches of the month of December and a new option to increase or decrease the ringtone volume.
OFFICIAL CHANGELOG
System
- Details optimized for Emergency Rescue
- Added a feature that supports reminders for private alerts
- Improvement of system stability and general bug fixes
- Security patches updated in December 2019
Phone
- Added a function to increase or decrease the ringtone volume for incoming calls
Reading mode
- New color effect for a more involved and comfortable reading experience with an intelligent color range and saturation adjustment (Settings> Display> Reading mode)
Downloaded from the following links:
OnePlus 6 – Download Open Beta 4
OnePlus 6T – Download Open Beta 4