When using vanilla shutdown (no Plymouth):
[FAILED] Failed unmounting /var.
After moving /var/log onto a separate partition, shutdown doesn't unmount /var due to systemd-journald using it.
Make journald log to a volatile location, so it doesn't lock /var. Caveat being there will be no shutdown logs.
Apply the fix:
pico /etc/systemd/journald.conf
Beneath [Journal]
, add:
Storage=volatile