Joining a restarted team says it is waiting
After you ask to join a team a member started again, the banner says you are waiting to be let in. Renaming a channel no longer marks it read.
When a team's Mac is gone and a member starts the team again, you get a banner to join the new one. Pressing it used to leave the button there, and pressing again showed an error. Now the banner says you are waiting for that member to let your Mac in, and the new team appears in your list once they do.
Renaming or archiving a channel from the team page also used to mark it as read, so you could miss new messages in it. It now stays unread until you open it.