Currently Jira Admins can view the various slack workspaces integrated on the Jira Cloud for Slack configuration settings:

However, there is no way for admins to directly fetch a consolidated report of all the connections established for each workspace / list of all projects that have slack connections configured. The project level connection details can only be fetched through the individual project settings. (Project Settings -> Apps -> Slack Integration)

It will be good to have on the UI, a site level listing of projects and their Slack connections for the Jira Admins to view and monitor.