This problem directly refers to the other question, but with some extra details:
Failed to open \EFI\UBUNTU\*garbled* - Invalid parameter
Also, I didn't find any real working answer out there and I'm not able to comment questions yet.
So, it started with switching from Windows 11 to Windows 10 on my system. I have dual boot with Ubuntu 20.04 that I really need for my work and Windows is for entertainment stuff. The very time I installed it the system booted to Windows without GRUB and it was the predictable behaviour. I felt very lazy to write another Live USB with Ubuntu and I haven't got the ISO by the time so I started googling about how to fix GRUB from Windows. Of course I ran into this solution:
bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi
It brought my GRUB back, but I've been facing another problem:
Failed to open \EFI\UBUNTU\smth - Invalid parameter
Failed to load image \EFI\UBUNTU\smth : Invalid parameter
start_image() returned Invalid Parameter - falling back to default loader
It wasn't much of a problem because I have to wait for extra 5 seconds and here goes the GRUB menu, but it's a really annoying thing when you have to switch OSs.
That's when I found the question mentioned before. I tried everything written there and also everywhere I could find info about this problem, but nothing helped.
So these are exactly the things I tried out:
update-grub2 - of course, the first thing to try. Useless here
boot-repair - works without errors, but gives no result
efibootmgr manipulations from this answer do not resolve my problem: https://askubuntu.com/a/1357432/1587722
Then I tried to do some more manipulations with bcdedit. No result, but I noticed that the default {bootmgr} path in my Windows 10 is /EFI/UBUNTU/SHIMX64.EFI. I can change it, but it will not have any affect because it's always shimx64.efi after reboot. I tried to find some info about not being able to change Boot Manager path, but not much luck. Secure Boot is already disabled.
Also, tried EasyUEFI software for Windows, because someone around here said I will be able to edit Boot Manager in Windows but it can only edit my Ubuntu entry, buttons for editing Boot Manager path for Windows entry are just blocked.
The default Windows mechanisms that should "repaire" the bootmgr do nothing too.
After reading a lot of related things and trying everything I could I came to opinion that it's probably the Windows-related thing because I have no idea why it keeps rewriting bootmgr path to shimx64.efi. Maybe there is an additional security mechanism or something? Any help will be appreciated.
