I downloaded elementaryos-6.0-stable.20210810.iso and wrote it out to an USB stick using Etcher. The resulting installer boots fine on a HP EliteDesk 8300 in UEFI mode, but fails to boot on 2 different Dell Optiplex 7020 machines. Tried both UEFI mode and Legacy mode, they both fail to boot. This is what is shown on the screen after selecting the UEFI USB disk to boot from:
Failed to open \EFI\BOOT\? - Not Found Failed to load image \EFI\BOOT\?: Not Found start_image() returned Not Found
The question marks are actually shown in inverse. This is shown for about 1.5 seconds, then the firmware boot menu comes back again.
If I try to boot the USB in Legacy mode, then a one liner says no bootable device, and press a key to reboot.
So it seems that whatever format this installer is using, cannot be digested by the Dell Optiples 7020 firmware (latest BIOS version, A18). As such, it is very likely to behave the same way on its sister models, the Optiplex 9020 and 3020 too. Would be nice if somebody having access to those models could confirm that.
Any suggestions on what to try?
Alternatively, how do I build a different installer that is likely to work with this fussy firmware? The Hera installer USB boots fine on these machines.