In addition to a new security patch, the update improves the stability of Camera. There could be more camera improvements which are not detailed in the changelog. The update carrying firmware version M315FXXU2BUC8 is rolling out in India with a package size of 549MB. 

  Galaxy M31 users in India who have not received the update yet, can manually check for the latest package by heading to Settings » Software update. [via]

New update for Galaxy M31 brings March 2021 security patch and camera improvements - 44New update for Galaxy M31 brings March 2021 security patch and camera improvements - 23