"Can support" and "antennas are present" are two different things.  If you have not removed the base cover to check, that's first.  If you purchase a card without having checked for the antenna leads and find them missing,  you will then be on the hook to purchase a new display assembly with them. The two cards Dell has drivers for are the DW5811e and DW5816e.  
Hi, I would like to use cellular with my laptop however this would require a WWAN card, I did some research and could not find any that would be compatible with the Dell Latitude 5490. Could somebody give me a hand, please? I rather purchase from a third-party other than Dell as most of them I found for other models were very expensive. Kind regards Lewis Brumby
Dell Latitude 5490 Compatible WWAN Cards