For archiving purposes we wanted to convert the json exports to a format that is slightly easier to read by humans.
So we developed a php script that takes the standard json export and splits it into CSV files for tasks/user_stories. With all attachments in a separate directory.
And a very basic html representation of the same content.
The script is available on: Convert Taiga json export to HTML and CSV · GitHub
Advice is to also keep the json files, so a prettier representation can always be created at a later date.