>I've been putting it in the Grub boot menu (on systems not afflicted with UEFI).
Modern Memtest86+, versions 6 and higher, support systems that boot using UEFI.
Yes, if a machine is afflicted with UEFI, and they no longer permit UEFI to be disabled, you can use that as a workaround.
Yes, if a machine is afflicted with UEFI, and they no longer permit UEFI to be disabled, you can use that as a workaround.