install syslinux

debian/ubuntu

apt install syslinux-utils extlinux

boot code install tool is there

    which extlinux
    ls -lF /sbin/extlinux
    extlinux -v

both mbr and efi images are there

ls -lF /usr/lib/syslinux/mbr/mbr.bin
ls -lF /usr/lib/SYSLINUX.EFI/efi64/syslinux.efi

from scratch

see syslinux-source