One UI 6 update is rapidly moving to every Galaxy Phones & foldables and Galaxy tablets are also in the race. Galaxy Tab S8 series is now getting One UI 6 version in India. It applies to all the variants including Galaxy Tab S8, S8 Plus, S8 Ultra, and their Wi-Fi variants. The new code X800XXU5CWL1 has been attached with new firmware.
It is still running on November security patch, though I guess in the coming days the Tab will receive December security code. It is huge 2800MB download file, so connect your Galaxy Tab S8 with the Wi-Fi.