EFI booting hangs

[Melab]

Is sda the external drive?

Yes, and it's the drive on which Linux resides that I have been trying to boot in UEFI mode.

Many systems promote an external drive on reboot to first drive when it is second drive when first plugged in.
You show Windows UEFI boot on sdb.

Ignore the Windows drive. It's irrelevant.

You show both UEFI & BIOS boot configuration. Often after updates only one or the other works.

Updates have nothing to do with this. My USB is setup so it can boot with both UEFI and BIOS. But this isn't relevant.

And then system UEFI/BIOS has to be set to match boot mode.

This distinction makes no sense to me. UEFI/BIOS settings literally IS where the boot mode is selected.

So always boot in UEFI mode.
But report did not show this which it normally does.
sudo efibootmgr -v

I've said ad nauseum that I CANNOT use efibootmgr on my fit-PC3 and that I CANNOT boot Linux in UEFI mode on it (I actually can, but see a few paragraphs below for clarification). If I could, then I would be in Linux, and if I was in Linux, then I wouldn't be having this trouble.

But if you can boot to grub menu, not a boot issue, but something after grub.

That's what I've been trying to say.

In grub menu remove quiet splash to see boot process. Often last line is not issue, but something before that.

Please see this post to see where the result of using debugging arguments.

Now, I can get Linux to boot in UEFI mode if I add "noefi", but this makes it so that the UEFI facilities are not accessible within Linux, which is not what I want.

Do you always have external drive plugged in?

I don't understand why you're asking these questions about the external drive. The external drive is a USB drive and it is the drive containing the Linux installation that I have been trying to boot.

UEFI usually removes or changes an entry for any drive that is removed.

Not relevant. I've been selecting the boot drive manually each time.

[Melab]

In post 29, you say: "Doing that presupposes that I have successfully booted Linux in EFI mode" in response to a suggestion to run efibootmgr. Possibly because in post 26 you say " I added the following boot options to the kernel command line and booted Linux on my fit-PC3 in EFI mode". So did you boot in EFI mode or not?

It didn't boot successfully, i.e., completely.

[oldfred]

External drives boot from the UEFI/BIOS one time boot menu, just like you boot live installer to do an install.
In UEFI/BIOS one time boot menu with newer UEFI systems you should have both a UEFI boot entry, if external drive configured for UEFI and/or a BIOS boot entry if MBR has boot code.
Some systems just have entries that say UEFIxx or xxx where xxx is the BIOS boot. The xxx is name or label of external drive.
Others may have two menus, a UEFI section & a BIOS section.
Not familiar with your system.

Can you boot live installer in UEFI mode?

[Melab]

External drives boot from the UEFI/BIOS one time boot menu, just like you boot live installer to do an install.
In UEFI/BIOS one time boot menu with newer UEFI systems you should have both a UEFI boot entry, if external drive configured for UEFI and/or a BIOS boot entry if MBR has boot code.
Some systems just have entries that say UEFIxx or xxx where xxx is the BIOS boot. The xxx is name or label of external drive.
Others may have two menus, a UEFI section & a BIOS section.
Not familiar with your system.

Can you boot live installer in UEFI mode?

None of that is relevant here. No, I cannot boot Ubuntu's installer in UEFI, but, again, I select which drive to boot from, not the system—no auto booting is used. Furthermore, we've already established that GRUB2 works fine, meaning that the problem is not with the boot selection screen provided by the UEFI/BIOS.

[oldfred]

Do not know much about Tiano, but years ago I thought it was a way to UEFI boot on a BIOS only system.
https://www.tianocore.org/about.html

[dragonfly41]

This is a long thread. Based on OP hunch (post #1) that this is a fit-PC3 issue I queried this in Google.

fit-PC3 EFI boot problem

A number of suggestions pop up.

[Melab]

Do not know much about Tiano, but years ago I thought it was a way to UEFI boot on a BIOS only system.
https://www.tianocore.org/about.html

Cool. Do you know of ANY boot arguments that might help?

[Melab]

This is a long thread. Based on OP hunch (post #1) that this is a fit-PC3 issue I queried this in Google.

fit-PC3 EFI boot problem

A number of suggestions pop up.

I wouldn't be asking for help here if Google had helped.

[dragonfly41]

So .. you have tried this suggestion gleaned from basic Google Search? ..

Reset the BIOS
Turn off the computer and unplug the power cable. Open the service door and remove the RAM memory modules. Short the test points TP136 and TP137 for three seconds to reset the BIOS. Reinstall the RAM and storage, close the service door, and plug in the power.

[Melab]

So .. you have tried this suggestion gleaned from basic Google Search? ..

Reset the BIOS
Turn off the computer and unplug the power cable. Open the service door and remove the RAM memory modules. Short the test points TP136 and TP137 for three seconds to reset the BIOS. Reinstall the RAM and storage, close the service door, and plug in the power.

1. I'm not going to mess with the hardware. I don't feel like risking anything.
2. I don't have a way to backup my BIOS settings, so I'm not going to throw away my settings on it.
3. I've reset the BIOS before and it didn't help.
4. I've been focusing on Linux and potential boot arguments.