Solved thanks to Reddit user liwindowsnux’s comment under a post by someone experiencing a similar problem on r/RockyLinux.
You’ll need a tool (such as Rufus) to burn the installer ISO into the USB stick in ISO mode (not dd mode) to get access to the /<USB_Stick>/EFI folder. I guess you can also use dd mode if you can get access to the EFI partition.
After the burning process, backup /<USB_Stick>/EFI to somewhere else just in case.
Get into /<USB_Stick>/EFI/BOOT, delete the original BOOTX64.EFI and BOOTIA32.EFI.
Rename grubx64.efi and grubia32.efi to BOOTX64.EFI and BOOTIA32.EFI respectively.
Boot your system with this USB stick in UEFI mode and you should be able to boot into the installer.
I am having the same issue both with the Fedora 37 live CD and Ventoy 1.0.82 (which uses the Fedora 37 shims). If I swap out BOOTX64.EFI and mmx64.efi with ones from either Ubuntu or Parted Magic, everything works great. I have also posted in Ventoy’s issues list here start_image returned Unsupported in v3.4 · Issue #18 · ValdikSS/Super-UEFIinSecureBoot-Disk · GitHub
and here is some of the hardware I have had trouble with Fedora 37 on:
MSI Z97A Krait Edition motherboard in custom build PC (BIOS version 2.0 and latest 2.3) with Secure Boot disabled error messages: Invalid image
Failed to read header: Unsupported
Failed to load image: Unsupported
start_image() returned Unsupported
then it reboots
Dell Latitude 7490 laptop (latest BIOS) with secure boot enabled error messages: Failed to open \EFI\BOOT\∎ - Invalid Parameter
Failed to load image ∎∎: Invalid Parameter
start_image() returned Invalid Parameter, falling back to default loader
but then continues to grub and works anyway
That’s an unnecessarily complicated way of doing it. All you need to do is write the ISO to a USB stick first, then just mount the relevant partition from the stick (the second one) and replace the files in a normal way - file manager, console cp, whatever. You don’t need to go to the trouble of modifying the ISO itself unless you need to write it to a DVD-R or something.
Unless I’m missing something, the partition is ISO9660 which is decidedly read only.
Believe me, I wanted it to be the case I could just copy a file over, but at least for a thumb drive made with dd, there was no way I could make that work. Even just replacing the shim on the ISO with xorriso before dd-ing wasn’t enough to make my board boot, the boot image jiggery pokery was required.
Perhaps Fedora media writer does something different? Perhaps I’m just dense. But believe me, I spent at least 3 hours trying to find a not complicated way.
The first partition on the stick is ISO9660. The second partition is FAT, and that’s where all the EFI bootloader files are - it’s an EFI system partition (it has to be, or else the stick wouldn’t boot). I just confirmed this with a stick I have here that’s written with dd.
I was sure the first thing I tried was replacing the shim on the second partition and it still refused to boot which was why I started down the road of ISO modification. But I just tried it, and it worked. Sorry for the noise!