Just as originally planned, Samsung is releasing the Android 8.0 Oreo update to its premium Galaxy Tab S3 slate. The update, bearing the build number T820XXU1BRE2, is seeding over the air in the UK but may be rolling out elsewhere as well - do you have a Galaxy Tab S3, check your software update status menu on the tablet and drop us a line if you have a pending update. The Android Oreo update brings the April 1 security patch as well as Samsung Experience 9.0. Source
Source: https://www.gsmarena.com/samsung_galaxy_tab_s3_gets_80_oreo_update-news-31045.php