This message was posted on behalf of Intel Corporation
Thank you for posting in Wired Communities. We do have two versions of I350-T4 server adapter, the previous version is I350-T4 which was discontinued, the current version is I350-T4V2 (https://ark.intel.com/products/84805/Intel-Ethernet-Server-Adapter-I350-T4V2) which have the AUX power component changes, this help to decrease the in-rush current during power supply start-up. However the product functionality does not change. You may refer to the Product change notification for more detail https://qdms.intel.com/dm/i.aspx/B3EAA66A-ED91-4822.../PCN113232-01.pdf
If you are installing retail Intel I350-T4 network adapter, you can use the driver available from our driver download site at
For OEM onboard NIC, we provide our driver to the board vendor and they are the one to customized the driver and post their driver on their website. With regards why the driver is not available from Dell* support this would be best answer by Dell support, we do not have control which driver version available on their website and please contact Dell to check if you can download drive from iDRAC.
Hope the above information help.