Please provide useful defaults for machine and cpu
Additional information:
See https://bugs.debian.org/1040212 and https://salsa.debian.org/helmutg/debvm/-/issues/15 for the preceding discussion and
https://salsa.debian.org/helmutg/debvm/-/blob/main/bin/debvm-run and https://salsa.debian.org/kernel-team/initramfs-tools/-/merge_requests/80 for the used machine and cpu values.