Also, how long does it take until I receive the authentication email?

Sorry for the confusion.

To avoid cold start, we wanted to sign up a sufficiently large group of people before opening the discussions. The site is scheduled to be opened on May 1 (you’ll receive an email notification).

There doesn't seem to be a way to propose new or non-traditional discussion topics

the discussion seems to be US-centric

The site is not officially open yet. So far, we just had several test runs with randomly selected people.