Flipboard is currently testing federation with a limited set of accounts. If your account was selected, you will see your fediverse username [@yourname@flipboard.com] on your profile and you will have received a “Welcome to the Fediverse” email if permissions are granted in your email settings.
Here is a directory of all Flipboard federated accounts.
If you have a Flipboard account and would like to test this new functionality, request to federate here.