Below is a note of how I install Ubuntu 18.04 LTS bionic to dell xps 13 5350
1. moving windows to virtualbox VM and reactivate.
2. update BIOS to 1.7.0 ( the latest ).
3. download and make live usb disk.
4. key: turn off BIOS secure boot, set SATA operation to AHCI, legacy mode boot instead of uefi
Hope this helps.
