Xiaomi has released V12.0.16.0.RFQEUXM to the Mi A3, a European build that contains the January 2021 security patch. The 12 MB update will arrive as an OTA on eligible devices, but recovery and fastboot zip files are also available.
https://www.notebookcheck.net/Xiaomi-issues-a-new-update-for-the-European-version-of-the-Mi-A3.598225.0.html