Unable to boot USB installer on Dell Inspiron 5420 AIO

[Dr. Zack Glantz]

I'd appreciate any insight if someone has ideas!

I've installed Chrome OS Flex on about 100 devices, and I've had a few issues that I've been able to troubleshoot.

I just purchased a few new Dell Inspiron 24 5420 All-In-Ones that I cannot get to boot the ISO to install Chrome OS Flex. I've tried all of the BIOS settings I can think of, I used a dd USB, and I've tried using Ventoy. I've also tried current and older ISO files.

Every time, I'm able to select the USB to boot from the F12 menu (or by adjusting the boot order in the BIOS settings). The Dell splash page shows up, but after about 2 seconds the machine freezes and power stops coming to the USB devices (USB stick stops flashing, keyboard backlight cuts out, etc).

I've also verified that it will boot a Windows ISO USB.

Does anyone have any brilliant ideas for how to get Chrome OS Flex installed??