One UI 3.0/3.1: Top new features for Galaxy devices [Video] - 9to5Google

Basically, in a bid to give Galaxy S21 some extras that older devices don’t have, there is a 3.1 build

The rollout of One UI 3.1 is not quite as widespread just yet, but we’re already seeing the Galaxy S20 FE get updated, so it hopefully won’t be long before previous devices fall in line