I've setup a UEFI core18 VM and dialed the memory all the way down to 256M but the loop mounting and loading of the kernel still works fine.
Then I've copied grubx64.efi from the core18 image to the core20 image and now QEMU no longer crashes. So it looks like a change in grub between 2.02 and 2.04 in combination with UEFI and 'low' memory is causing this issue.
I've setup a UEFI core18 VM and dialed the memory all the way down to 256M but the loop mounting and loading of the kernel still works fine.
Then I've copied grubx64.efi from the core18 image to the core20 image and now QEMU no longer crashes. So it looks like a change in grub between 2.02 and 2.04 in combination with UEFI and 'low' memory is causing this issue.