If you didn’t install Qubes OS on removable drive then there is no need for you to copy grub files to /EFI/boot/ directory. Just restoring UEFI entry with efibootmgr command should be enough.
running the efibootmgr command you listed before gives the following result:
BootCurrent: 0001
Timeout: 0 seconds
BootOrder: 0000,0001
Boot0001* UEFI: USB PciRoot(0x0…etc
Boot0000* Linux HD(1,MBR,…etc
Did you change /dev/sdb and EFI System partition number in efibootmgr command to your Qubes OS drive name/partition?
You can find out the correct drive name/partition with these commands:
From this output it seems that the command wasn’t executed correctly and there was some error in the command. Check that you don’t have a typo in command.
Are you sure that /dev/sda is your Qubes OS drive and not Qubes OS installer USB drive?
Can you post the output of this command?
lsblk -o NAME,FSTYPE,SIZE /dev/sd? /dev/nvme?n?
After you run this command: efibootmgr -v -c -u -L “example” -l /EFI/qubes/grubx64.efi -d /dev/sda -p 1
Do you see the new boot entry with the name example in the command output? You can also run efibootmgr without arguments to print all boot entries.
Also, just in case, the -l argument in efibootmgr is lowercase L.