How to configure Grub2 to be able to boot alternatively on UEFI or BIOS mode

This article describes how to remediate to the boot issues encountered when switching a RHEL7 or later system from UEFI boot to BIOS mode (aka Legacy). This article additionally proposes a Grub2 configuration setup that enables booting alternatively on UEFI or BIOS mode, which is very useful when deploying an unified image to different hardware.

For demonstration purposes, we will use a...