What is the main purpose in notifying data subjects of a data breach?

The main purpose in notifying data subjects of a data breach is to allow individuals to take any actions required to protect themselves from possible consequences, such as identity theft, fraud, or discrimination. This is consistent with the principle of transparency and the right to information under the GDPR. The other options are not the main purpose of notification, although they may be secondary effects or benefits of the process. References:

Data protection impact assessments | ICO

[Art. 34 GDPR – Communication of a personal data breach to the data subject - GDPR.eu]