Comment 1 for bug 1918996

Please try with a newer efi-pack (it works for me in version 18.04 LTS of all Ubuntu family flavours (including Kubuntu). I use usb-pack_efi-2.02.tar.xz which matches "1" in the menu in 18.04 LTS.

If you try to use mkusb with 'too old' versions of Ubuntu, you may have problems. I would recommend that you stay with currently supported versions of Ubuntu. mkusb may or may not work with older versions of Ubuntu (there is no maintenance for end-of-life versions).

If you want to explore end-of-life versions of Ubuntu, I suggest that you try some other tool to create USB boot drives, for example Unetbootin.