Just like in the Contacts or Messages app on the OnePlus smartphone, we can set a light or dark design in the browser app, which is much easier on the eyes when navigating the Internet, where all light tones of the layout turn into a dark surface.

Note: In addition to activating the desired design, the system default setting can be set if a schedule of the dark design has already been programmed.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Chrome app
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  Theme
Step 5:  Choose  System default ,  Light  or  Dark
  1. Open the Chrome app
  2. Open the menu
  3. Open the Settings
  4. Tap on Theme
  5. Choose System default, Light or Dark

OnePlus Instructions