Under a brand new Tumbleweed system, using virtualbox installed directly from the default repo, when vagrant up tries to create the virtual disks, errors are thrown (and the process aborts) due to problems with an unknown 'SCSI Controller'. (Sorry I don't have the exact error text handy). By tweaking the argument to --storagectl in the storageattach command in the Vagrantfile to 'SCSI' (instead of 'SCSI Controller'), I was able to get past the error. It would appear that VIrtualBox has changed the name of the storage controller.