Previous information indicated that the Redmi Note 8 would get the Android 10 update with MIUI 12 shortly. That may be in doubt now, however, as word from the Mi Forums claims the MIUI 12 update for the Redmi Note 8T—essentially a Redmi Note 8 for certain markets—is months away.
https://www.notebookcheck.net/MIUI-12-update-for-the-Redmi-Note-8T-potentially-months-away-may-be-same-for-the-Redmi-Note-8.478878.0.html