Non-Windows machines are currently considered "devices" in Lansweeper. We recommend creating a separate report for these using tblCustDevices, as it is currently very difficult to create a report that includes both computers and devices.
In Lansweeper 5.0, which is currently in development, computers and devices will be merged into a single "asset" category, which will simplify the kind of reporting you are trying to do. We expect to have a 5.0 beta release ready by October.
A basic device report can be seen below.
Select Top 1000000 tsysDevicetypes.ItemTypeIcon10 As icon,
  tblCustDevices.Displayname As [Device name], tsysDevicetypes.ItemTypename As
  [Device Type], tblCustDevices.Model, tblCustDevices.Vendor,
  tblCustDevices.Location, tblCustDevices.Ipaddress, tblCustDevices.FirstSeen,
  tblCustDevices.LastSeen, tblCustDevices.DeviceKey, tblCustDevHD.Filesystem,
  tblCustDevHD.Size, tblCustDevHD.Used, tblCustDevHD.Available
From tblCustDevices Inner Join
  tsysDevicetypes On tsysDevicetypes.ItemType = tblCustDevices.Devicetype
  Left Join
  tblCustDevHD On tblCustDevices.DeviceKey = tblCustDevHD.DeviceKey
Where tblCustDevices.State = 1
Order By tsysDevicetypes.ItemTypename, tblCustDevices.Displayname,
  tblCustDevHD.Size Desc