Description of problem:
Writing the Fedora CoreOS Installer ISO to a USB stick does not yield a bootable image.
DD and Fedora Media Writer will write the image, but it won't boot. Gnome Disk Uitl complains that the image does not appear to be a live image or installer DVD.
Version-Release number of selected component (if applicable):
Always: Download installer iso, write to USB stick, try to boot in a machine.
I am sorry, one correction: the complaint about the image not being a live image is from livecd-iso-to-disk, not the Gnome Disk Tool.
Thanks for the report! Booting the ISO from a USB stick isn't working on BIOS systems because we aren't currently adding an MBR. https://github.com/coreos/coreos-assembler/pull/677 should fix this.
livecd-iso-to-disk is not expected to work with Fedora CoreOS ISOs, since Fedora CoreOS doesn't lay out its ISO images in the way that livecd-iso-to-disk expects.
This should be fixed in an upcoming Fedora CoreOS release.