https://wccftech.com/oneplus-7-pros-zen-mode-and-screen-recorder-is-now-available-for-older-oneplus-devices/

With each subsequent OnePlus release, there come a host of new features that remain exclusive to the device for a period of time. They do, however, make their way to older devices via updates. This time around, the company announced some new features such as the Screen Recorder, Zen Mode, and NightScape 2.0 with the new OnePlus 7 and OnePlus 7 Pro. Shortly after the announcement, the company has promised to release the Zen Mode and the Screen Recorder on older devices. Nightscape 2.0 will be left out owing to ‘hardware limitations’

Ideally, one would have to wait for the features to arrive on devices via future OxygenOS builds. But, it is now possible to install the unofficial versions of the Zen Mode and the Screen Recorder, courtesy of XDA Developers. All you have to do is download the APK and install it. Here is the Zen Mode APK and the Screen Recorder APK. All you need is a OnePlus device that is running Android Pie (which is pretty much all of them, except the 3/3T). Once you’ve installed the apps, they can be accessed from the quick toggles tray. Do note that they will not be visible in the App Drawer.