New Channel Announcements
When people create new channels within a team, it would be great to have a popup that shows team members within the channel a screen something like "New Channels created since your last visit, refresh, etc..."
What we are finding is people are creating new channels within Teams, yet no one knows about them unless they click on the More link within the team.
There are some plugins for this request.
Maruyama Takayuki commented
FYI, my coworker created "New Channel Announcement Bot" in https://github.com/tsyki/mattermost-channel-add-checker