Unable to boot ubuntu 19.10 or newer on dell xps 9570

Hi,

Since updating my dell xps 9570 (latest BIOS 1.15.0 and a few previous versions) from 19.04 to 19.10 I have been unable to boot ubuntu. It fails with the following error quickly flashing:

  error: file `/boot/` not found

Then followed by:

  error: cannot allocate kernel buffer.
  error: you need to load the kernel first.

  press any key to continue...

This occurs when doing an update from 19.04 to 19.10 and also when just booting off a usb drive with 19.10.

When booting off the usb drive. The first error flashes quickly before displaying the usb installer options. Selecting any install / boot option results in the second error about kernel buffer.

I have tried all combinations of bios settings I can think of, such as toggling secure boot and other options. The only thing that made a difference is booting via USB with LEGACY EXTERNAL DEVICE BOOT. This allows the installer to complete, but I cannot then boot off the hard drive.

I have tried the same USB drive with 19.10 on a Dell XPS 7590 with BIOS 1.2.3 and the USB stick boots fine. I have also tried many different USB drives on my 9570.

I have tried a few daily builds of 20.04 with the same result. Most recently I tried the current version 2020-03-24 09:40.

Note: 19.04 and earlier continues to work no problem.

I have asked on askbuntu.com and not found a solution https://askubuntu.com/questions/1183129/19-10-usb-installer-boot-fail

Update: Tested with 20.04 beta and same result.