Maybe something like @harvard-school-of-journalism.com, although that's too wordy. The article mentions "Harvard Extension School", so, it could be some variation of that.
Edit: I tried harvard-extension.school in the browser, it redirected me to http:harvard-education.edu (not https!), which seems to be a clone of extension.harvard.edu . The WHOIS records of harvard-extension.school/.education are pretty new (registered last year), and they're registered on GoDaddy and 1API GmbH respectively. A Germany-based registrar? Would Harvard use them?