Using the reports 'Device Inventory', 'Devices', 'Devices by user' - Not one of them has the column for ICCID number so I cannot report on sim numbers attached to devices.
How can I add this to the reports?
Reports are fetched according to the configuration set by the development team. Unfortunately, this cannot be modified. However, you can export the complete card of the device manually for each device from device properties. You can vote for this existing feature request so that our development team can look into it and consider it for furture release.