Other than a new security patch, the changelog also mentions some bug fixing and system stability improvements. This is a minor security patch update and does not brings new features or UI changes. The latest update for OnePlus 6 and 6T is still based on Android 10 and users are desperately waiting for the Android-11 based OxygenOS 11 update. It seems, users will need to wait a bit longer to receive the update.
OnePlus 6 and 6T OxygenOS 10.3.10 update : Changelog
System Updated Android Security Patch to 2021.04 Fixed known issues and improved system stability
As usual, the OTA update is rolling out in a staged manner which means that it will initially reach a small percentage of users. Once the company confirms no critical bugs in the build, then it will roll out on a broader scale. [source]
