Steam DLC and the EA app

L0velyBr0kenN1xx  If you're still trying to do this, there are a couple of approaches you can take.  One is to temporarily (or permanently, if you prefer) unlink your Steam and EA accounts, and perhaps clear the EA App's cache afterwards:

https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/

The other is to try to buy the content on the EA website.  Google the names of the pack(s) you want and find their product pages.  I am not completely sure this will work, in that you may still be directed to Steam, so try one stuff pack or kit first.  If the EA App still tells you to install through Steam, then unlink your accounts and try again.