hear (about)

Thanks for your letter. I haven’t heard about you for a long time.
Thanks for your letter. I haven’t heard from you for a long time.

If you hear about someone or something, you receive information or news about them: ‘Have you heard about Peter’s new job?’

If you hear from someone, that person contacts you by phone, email, message, etc.: ‘I haven’t heard from Peter since he moved to Canada.’