The image is called "chorus image" and is on thecdn.vox-cdn.com.
OneUI 4 is starting to be rolled out again.
The photo was taken by Chaim Gartenberg.
The OneUI 4 update was paused due to reports of bugs and soft bricks from users, but is now rolling out again. The update should be available for the S21 phones, along with the Z Flip 3 and Z Fold 3.
Material You, a design by the same company, was the basis for the visual redesign in OneUI 4. An updated keyboard is also included. Users said they were getting poor performance, screen flicker, and other bugs despite the public release of the device. The company stopped rolling out the update to South Korean customers because of an issue with the Play Store. The roll out is back on.
There have been some issues with the release of the Android 12.
Other manufacturers have had trouble with the release of the Android 12. The OxygenOS 12 update for the 9 and 9 Pro was stopped after reports of bugs.
The update meant to fix the bugs in the Pixel 6 introduced new issues that are still being worked on by the company. Older versions of the OS are available for the 3A, 4, and 5A. Some users have reported issues on those phones, but they seem to be less bad than those experienced by the other users. The December update for the operating system doesn't seem to have made it to most people's phones.