The ISO used is a modified version of the Online version (no repositories bundled in the CD) with updates (SLE-15-SP6-Online-x86_64-QU1-Media1.iso) available in https://www.suse.com/download/sles .
The only modification done is to set the "timeout" variable in /boot/x86_64/loader/isolinux.cfg to 0, so that the KVM does not automatically boot from disk after a timeout if the user does not press a key (which was a problem that we found while testing this distro that made difficult to install it).