Samsung has not yet launched a stable Android 11-based One UI 3.0 update for several Samsung smartphones. As of the current progress, it may take several weeks for the company to provide a stable version.
Samsung has already launched the One UI 3.0 update, it is time to start discussing the One UI 3.1.
Samsung launched the Galaxy S21 series. So far, as far as we know, the Galaxy S21 series is running One UI 3.1 based on Android 11.