Update: Rattle is gone!
Now I still need to do the other 3 doors with some insulation... and the rear seats, and the trunk area... and everywhere else
Haven't been able to see the new ambient LED yet because of the long days.. but I'll take some pics of them soon. Installation was very easy.
Strange that in the near 8 years I had my Cupra 280, it never had any door rattles.