It's just yahoo groups that requires your phone number.
I cannot believe this stupid app is so popular when you can't even monitor multiple servers at once! When every brother and their mother has a discord server but I can only look at one channel on one server at a time??
However I like that I can see all the channel with unread messages at once, and can switch between them quickly. On Discord if I'm chatting in three channels spread across two servers then switching takes two clicks.