How to manage structural changes (ALTER) to an existing database?

**Question**
It has often happened to me (fortunately so far only before the distribution of the app but it could also happen after), having to modify the database structure by adding new columns.
The problem I encounter every time is that, especially if the new fields are not NULLABLE, the app crashes on startup because empty values are found in the fields.
What is the correct way to avoid this problem?

**Version**
- Platform: iOS, Android
- Flutter version: 3.3.10
- Hive version: 2.2.3

Start by reviewing Hive 2.2.3's documented approach to structural changes and schema evolution for Flutter apps on iOS and Android. Document the supported process for adding columns, especially non-nullable fields, and show how an app can start successfully without empty-value failures.

Written by the indexing model from the issue text.