Since this thread is getting round many of the bases, another part of the picture... efibootmgr
This shows the state of the non-volatile memory boot variables. The UEFI should use these to work out which drive and efi executable to go to first. This used to be important for dual boot with Windows, because a Windows update would mess with them sometimes; I don't recall users here on KFN reporting this for a couple of years or so.
Code:
sudo apt install efibootmgr sudo efibootmgr -v
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