Magnum needs a image in glance to use when it spawns masters and workers. In Victora, Fedora CoreOS 33 is the version the project test against, and thus is the version we need to use 
# Download image
Browse here https://builds.coreos.fedoraproject.org/browser?stream=stable&arch=x86_64
# Decompress
xz -d <image.qcow2.xz>
# Convert
qemu-img convert -f qcow2 -O raw <image.qcow2> <image.raw>
# Upload to glance. Note the properties. These are important
openstack image create \
--disk-format=raw \
--container-format=bare \
--file=<imagw>.raw \
--min-disk <big enough> \
--property os_distro='fedora-atomic' \
--property hw_rng_model='virtio' \
--public \
--protected \
fedora-coreos<version>-stable