Yyeeaahh !! It connects !
Ok, so what I did is to go back to windows, and grab the settings (took a picture with my tablet) and then restart Qubes and apply it dot by dot
So apparently the gateway was the wrong one, it was the gateway of my server rather than the gateway for the laptop. Anyway, it does connect with wire now.
I guess I will never know why Qubes refuses to connect with DHCP, but I’m good with it as it is. It’s a fixed IP on my server anyway.
Ok, now, dealing with security, a secure install (my other thread) and secure connection (VPN and Tor)