Centos 8 on external drive cannot be recognized by another PC

[lql341]

Hi guys,

I just installed a Centos 8 on my external hard drive. It worked well on both of my computers (ASUS K46C and Dell Inspiron 15 7000 gaming). But when it was plugged in my friend's computer (another Dell product with legacy boot). It cannot be recognized. I navigated to BIOS settings, changed the bootable priority but there was no Centos Grub option. It directly went to Windows 10.

BTW, my ASUS has a legacy bootable way with the secure boot mode off, and my Dell has a UEFI boot with secure boot mode on. Both of the setups work, I don't have a clue here. Maybe because my computers are dual systems while my friends' only has a Windows?

[BShT]

there are n^n variables that can make it work or not

there is no magic answer