Not booting after motherboard replacement (XPS 15 9500) - (Solution)

[Michael Bonert <michael.bonert@utoronto.ca>]

Issue: "No bootable devices found" after motherboard replaced
Background: previously functional Debian system where hardware quit  
(so called "No POST").

I spent a few hours on a "No bootable devices found" issue:
The fix was in the Dell BIOS (got to by pressing 'F2'):
-> Boot Configuration
--> Add Boot Option
---> [select the SSD] (the BIOS then reads the "EFI" partition)
----> one then needs to select the "grubx64.efi" file + give the "Boot  
Option" a name, e.g. "Debian Linux on SSD"
-----> Save changes to BIOS + Exit BIOS

The above presumes: the SSD is intact and has an EFI partition with  
Grub on it.

I was looking at the re-installing GRUB (  
https://wiki.debian.org/GrubEFIReinstall )... that isn't the solution  
here.

The fix is two minutes if one understand what is happening.  Perhaps,
this will save someone else some time.

System: Dell XPS 15 9500
OS: Debian Linux 10.10 (stable) **only**
~~

Other BIOS settings important for Debian Linux on XPS 15:
    Boot Configuration
        Enable Secure Boot [x] On
            --> CHANGE THIS TO 'Off' (from "On")
    Storage
        SATA Operation -> RAID On
            --> CHANGE THIS TO "AHCI" (SATA is configured for AHCI mode)
    Pre-boot Behavior
        Fastboot [x] Minimal
            --> CHANGE THIS TO "Thorough" (from 'Minimal')



Michael