I installed the most recent 

kernel-default-5.3.18-lp152.72.1.x86_64
shim-15.4-lp152.4.8.1.x86_64
grub2-2.04-lp152.7.25.1.x86_64

on my Dell Precision 3620 this week and rebooted as required. The system
doesn't come up but shows "system is compromised" for a second, followed by
power down.

If I change from "UEFI with secure boot" to "UEFI without secure boot" it
behaves well again and just boots.

I've set "mokutil --set-verbosity true" as advised which outputs a lot of
messages, I unfortunately have no serial console at hand to connect and save
them. I'll try to attach a video from the screen that shows the boot process
and messages.