My answer: You have to take yet another "we'll send you an email" step, asking for a "magic link" for your mobile devices even though you're on your desktop machine, and click that, then there are channels. By the way, that magic link they say is only good for 24 hrs will expire in just a few minutes so be quick. From there, you're on your own. Good luck.
To answer the original question, clicking on Direct Messages
, I counted 28 people in https://quantopianusers.slack.com now.
Then later I saw a banner like: "Your team is now 80 members strong, with 5411 messages sent across 6 channels". That text was not copyable. Only 3 channels showing under Channels
. Click it to show and join more. I guess maybe writing things for a user perspective isn't as easy as I would think it could be. Wishing slack well and all the best.