Here is to let everyone know that the Inspiron 14 7490 does not accept Kubuntu (or ubuntu itself).
Explanation https://www.dell.com/community/Inspiron/Inspiron-7490-BIOS-How-to-turn-off-intel-RAID-on-and-swith-disk/m-p/7436820/highlight/true#M70243

And from Customer service yesterday :
j’ai le regret de vous informer que votre commercial refuse de retourner l’ordinateur/l’échanger car la commande est conforme au bon pour accord.
Meaning : the sales person refuses to exchange or return the order since it is compliant to the sales agreement.

Hello unfortunate Dell 7490 users,
There is a solution : https://forum.ubuntu-fr.org/viewtopic.php?id=2064635
as always with linux and its great community