I'm trying to put an ArchLinux install onto a USB-HDD and want it to be bootable on BIOS systems as well as on UEFI systems that use secure boot. Therefore I have one main question.
Does an UEFI system with active secure boot permit or deny booting from USB drives?
According to this article the UEFI partition holds all the bootloaders for the OSes on a physical drive and in my scenario that partition would already exist elsewhere on the system.
On the Arch-Wiki I found this article on basic decisions to use rather MBR or GPT for partitioning on the boot device (also applicalbe on USB drives) and possible bootloaders are listed here but will any of these be recognized by the UEFI Firmware?