Error added: 2021-07-20T22:45:07Z
My /etc/mdadm/mdadm.conf file hadn't been modified since it was installed. It specified devices by /dev/sda1, /dev/sda3 etc, so I figured it was just complaining that I wasn't using the UUID system of identifying drives. Therefore, I backed up the system remotely, rebooted it, and it came back up fine.
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