Uros Milanovic gives us a heads up:
Advance notifications allow you to prepare for planned maintenance events on your SQL Managed Instance resources. They alert you 24 hours before a planned maintenance event. Advance notifications work hand-in-hand with SQL Maintenance Windows – with the two combined, you gain control over when your managed instances receive updates and receive a notification ahead of time.
Read on to learn more about how this works. There is a bit of setup involved to subscribe to these, though Uros provides a link to a guide on how to do it.