No.
Rich Text fields from Salesforce objects such as Opportunity, Account, Contact, or custom objects cannot be downloaded in Rich Text Format (.rtf).

  • Rich Text field content is exported only as plain text in the CSV file. If you download Lightning Notes.
  • Formatting elements such as bold text, hyperlinks, images, and bullet points are not retained.

Supported: Lightning Notes
Not Supported: Rich Text object fields as 
.rtf