Originally Posted by
le Pingouin
Not sure about SD cards but usually there needs to be a USB drive plugged in for it to show as a boot option.
SD cards are fine, just need to get into the BIOS and enable boot first from "other" depending on BIOS nomenclature or interrupt the boot process to get to "select boot medium". All my computers are set to boot first from USB/SD then DVD and last from internal disk. If it is a fairly modern machine with UEFI "legacy boot" may have to be enabled for some Linux variants.
R6A I've been a Linux user since 1993 so PM me if you need help.