A couple of days ago, OnePlus announced the end of the OxygenOS Open Beta program for the OnePlus 6 and 6T. However, the duo is scheduled to receive bi-monthly stability and security updates until at least mid-2021.

The latest stable release, OxygenOS 10.3.3 brings the April Security Patch to the devices. The update also includes VoLTE and VoWifi support for Telenor in Denmark and VoWifi support for Reliance Jio in India.

Here’s the complete OxygenOS 10.3.3 Changelog for the OnePlus 6 & 6T:

• System
  • Fixed the issue with a black screen randomly appearing while playing games
  • Updated GMS package to 2020.02
  • Updated Android Security Patch to 2020.04
  • Improved system stability and fixed general bugs
• Network updates
  • Integrated VoLTE & VoWifi support for Telenor – Denmark
  • Integrated VoWifi support for RJIO – India
• Cloud Sync updates [India only]
  • Updated the CloudService to Version 2.0

Source: OnePlus Forums