Update 6 – December 07, 2022: AT&T also released the Android 13 update for the S21 series in the US.
Update 5 – December 01, 2022: Verizon released the stable One UI 5 update for the Galaxy S21 Ultra in the US.
Update 4- December 01, 2022: Samsung Galaxy S21 is now getting a stable One UI 5 update in Bangladesh.
Update 3- November 29, 2022: T-mobile also started rolling the Android 13 update for the locked Galaxy S21 series in the US.
Update 2- November 22, 2022: Samsung Galaxy S21 Series is now getting One UI 5 stable update in Canada with the firmware version DVK3.
Update 1- November 07, 2022: Samsung has finally started sending the One UI 5 (Android 13) software for the Galaxy S21 Series in Europe. Earlier, the company shared the schedule of the One UI 5 upgrade plan in which the Galaxy S21 lineup was listed to get a stable Android 13 update in November 2022.
Finally, the stable One UI 5 (Android 13) update for the Galaxy S21 lineup comes with Stackable widgets, Better Samsung Privacy Hub, New notifications UI, Recognize text anywhere with OCR, Multitasking gestures, Pro Mode camera helpers, Better accessibility options, Note-taking during calls and more.
— SamLatestUpdates (@latestsamupdate) November 7, 2022
You can download the stable One UI 5 update in your Galaxy S21 by navigating to Settings -> Software update -> Download and install.