In order to install Ubuntu on the XPS 7590 (I've heard the same was true for the 9570 as well) you have to open the boot menu and modify BIOS settings to turn "Secure Boot" off and to switch SATA mode from RAID to AHCI.
Doing the above I was able to fully install Ubuntu 18.04, however I needed a hard-wired internet connection to handle any downloads/updates because, under the WiFi settings no networks were available and I was instead greeted by the message "No WiFi Adapter Found". None of the existing answers on this forum, StackOverflow, or even working with Dell Support were able to solve this issue for me.