Why would you want to shut down your slack space? Some projects use a slack space and even the ASF has one: the-asf.slack.comI was asked to shut down all NuttX project communications that are not publicly visible. I have done that. It was a slow gradual phase out, described in the Google group.
I did create a #nuttx channel in the ASF slack: https://app.slack.com/client/, but it has been recommended that we not use that Slack for communication either.