@BreakingBad you are breaking it badly 
.
Here is your real problem:
You were almost there, almost remembered, but not completely:
This flag should have been on sda5 (unknown=unformatted?). It’s this:
When you need to install grub in MSDOS_Legacy mode, on a gpt drive, you fake the MBR target, creating a small partition and do not format it at all, only applying the bios_grub flag. Then you install grub, with an MSDOS/Legacy grub-install command, targeting the sda drive (like normal), not the partition (sda5). Grub would find it by the flag.
From your long adventure’s story telling, it seems:
- The only UEFI type booting is done with your Hackintosh
- All other systems (Debian, WinOS, EnOS) are on MSDOS_Legacy
- Grub customizer is still a destroyer application (for adventurous users, since many users use it in a simple way).
Actually, when you remove the package, the /etc/grub.d/* drop-ins are not removed/deleted. This created the extra mess.
You missed this description from your story:
It might have helped someone to identify the issue (from the errors/messages).
As for your questions:
Yes. No UEFI. No systemd-boot. No rEFInd.
Yes, but fake, as explained above.
Yes. No.
It was (probably) installed on sda5, as explained above.
Possible solution:
- Boot with EnOS Live installer image in MSDOS_Legacy mode
- Use Gparted to apply
bios_grubflag on sda5 (the small unformatted partition) - Chroot to EnOS installed system, mounting only the root partition (sda4)
- Remove/uninstall grub-customizer
- Delete/rename
/etc/grub.dfolder - Re-install grub package
- Install grub for legacy, on sda (no need for
sudoin chroot)
grub-install --recheck --target=i386-pc /dev/sda
- Create grub config.
Good luck! 