Unetbootin is FURIOUSLY difficult to install on Ubuntu, Debian and even Windows.
I tried the ~5MB unetbootin-linux-xxx.bin file which FAILED.
I tried the ~23MB unetbootin-linux.tar.gz source code which FAILED.
I tried WinUSB which failed.
I tried to get USB-Image Writer, which also failed.
Finally found Etcher, fully open source bootable SD & bootable USB image writer. Even better than standard dd method which lacks progress information.
Grab it here on Windows, Linux, even Mac: https://etcher.io/