From v8 to v9

Ensure your config/backup.php file is in sync with the latest settings. You can copy paste the missing defaults from this config file.
All keys in the config file are still snake_cased. Rename any camelCased keys to their snake_cased counterparts

From v7 to v8

There are no changes to the public API. You can upgrade without having to make any changes. The package now requires Laravel 9

From v6 to v7

All notification class names got suffixed with 'Notification'. Make sure you update the classnames where you are using these notifications.

From v5 to v6

All keys in the config file are now snake_cased. Rename any camelCased keys to their snake_cased counterparts.
Make sure the structure of your config file is the same as the one that gets published by the package.
The health_checks config keys now contain actual check classes. Modify your config file so it uses the actual check classes.

From v4 to v5

The config file has been renamed. Change the name of the config file from laravel-backup.php to backup.php