Install Ubuntu 18.04 on Dell XPS 15 9570

I am trying to install Ubuntu 18.04 on my Dell XPS 15 9570.

I have followed the steps provided in the official tutorial.

However, I have stumbled on an issue.

1. When I boot from USB I am immediately directed to the "Try Ubuntu" option. I do not manage to choose "Install Ubuntu"

I connect to WiFi here. And then open the Install Ubuntu 18.04 icon from the desktop.

2. I select the language and the keyboard

3. I then press "Continue" on the following window:

4. I get to the following window:

If I try to press "Install Now" it tells me: When I try to press "change" or "+" the Install window closes.

I suspect the issue is that I need to change the drive to ACHI mode. But, I don't know why that would help and why can't it see the drive now.

I have create the bootable USB using Rufus 3.3 and then I have formatted it and tried again using UNetbootin. Same issue.

With the help from @oldfred, I have solved the issue and installed Ubuntu 18.04 by going through the following steps:

1. Changed the driver from RAID to AHCI
2. Disabled Secure Boot
3. (Might not be needed) shrank the Windows partition