The Users Report provides visibility into all users in the system, with the capability to filter by username, email, or whether the user is active.
There is also a Show User Permissions checkbox to see object permissions for the user based on their group membership. This adds a column for each permission type and lists all objects for which they have the permission. For FlexDeploy Administrators, content for all permission columns is simple "All". Note that this report only shows Global permissions and not project/folder/release level permissions.