http://multibootusb.org/page_download/
Stuck at “Installing Syslinux…”?
source: https://github.com/mbusb/multibootusb/issues/361
https://github.com/mbusb/multibootusb/blob/master/data/tools/gptmbr.bin
and saving in under
/usr/share/multibootusb/data/tools
You may need this:
sudo apt-get install qemu-kvm qemu virt-manager virt-viewer