Lesson, delete everything on the partition that you want to make boot disk... Problem came from the boot disk instead of of Ubuntu and Dell I've tried many time with ubuntu-16.04.4-desktop-amd64.iso . The ubiquity crashed with some errors  debian-installer/locale doesn't exist Upgraded ubiquity as comment here https://askubuntu.com/questions/1033179/ubuntu-18-04-installer-crashes-on-dell-xps-15-9560 But no successful. I even tried with 16.04.4... … Đọc tiếp Install ubuntu 18.04 on Dell Latitude 7490