Although the new stable MIUI ROM for the Xiaomi Redmi Note 3 carries the build number 9.2.4.0, it still uses a Marshmallow core. Sadly, it seems that this Snapdragon 650-powered handset will never get Android Nougat.
https://www.notebookcheck.net/Xiaomi-Redmi-Note-3-gets-MIUI-9-but-no-Nougat.280568.0.html