Using WiFi my SOT can be anywhere from 10-13hours on a full charge with moderate usage, on mobile data it's around 8-9hours. That's with WQHD+ 120hz, Bluetooth, NFC enabled etc.
According to the battery section, a full charge will last me 2 days and 2 hours. My Galaxy Tab S6 lite has 6000mah battery and has less SOT per charge than the s21 ultra - somehow.