I have tried all of the perms and combs of secure boot, boot options, legacy and UEFI as far as I can see. It still fails to offer me an option to boot from anything except Windows boot manager (P0: ST1000LM024 HN-N101mbb). There were two other options which I think were the CD rom and the HDD but they went missing when I changed to UEFI only and then back to UEFI and Legacy. An example of "how to" I saw on the WWW showed many more devices to choose from but I can't persuade them to show them selves.
I have put a Linux boot SD card in the slot but it doesn't offer me it?
if I intercept boot with F10 it offers me the Boot Manager, the CD Rom and the HDD. There still is no option to select SD Card boot source.