I aimed to run desktop-installer in a guest with 13.0-RELEASE. Problems with file systems before installation began:
After supposed repair: the bad file descriptor symptom recurred with the UFS boot volume, I couldn't enable soft update journaling.
Postscript
FreeBSD bug 259090 – UFS: bad file descriptor: soft update journaling can not be enabled on the FreeBSD-provided disk image for 13.0-RELEASE – failed to write updated cg
After supposed repair: the bad file descriptor symptom recurred with the UFS boot volume, I couldn't enable soft update journaling.
Postscript
FreeBSD bug 259090 – UFS: bad file descriptor: soft update journaling can not be enabled on the FreeBSD-provided disk image for 13.0-RELEASE – failed to write updated cg