The new update for Galaxy M31 is rolling out in India which can be identified by firmware version M315FXXU2BUF1. This is a minor security patch update and does not brings new features or UI changes, but it improves the system stability. It’s good to see mid-range Galaxy M-series phones getting the latest security patch.  The June 2021 security patch for Samsung phones brings 19 fixes from Samsung and 47 fixes from Google for security and privacy related enhancements. The update should reach your Galaxy M31 with a pop-up notification if you live in India. To manually check for the latest update, navigate to Settings » Software updates and then tap on Download and Install. [source]

M315FXXU2BUF1   Galaxy M31 June 2021 security patch update - 30