Fri, 22 Mar 2019 13:58:50 +0000,

if you're lucky try removing and re-seating the PCIe card in case it's a
loose contact, but other people seem to have either failed capacitors or
a mismatch of PCIe generations between the card and the motherboard

I am confused.

The PCIe slots are the black unused slots I think where there is only one
card, which is that RAID card you indentified.

I did move the RAID card from the leftmost long white slot to the rightmost
long white slot and that "helped".

Both errors remained but at least the machine booted to CentOS after I did
that switch (and also reseated all cables, blew all dust out, rebooted, so
it could be any number of things that allowed the machine to boot to
CentOS).

My main confusion about the SATA 0 unknown is whether it's the 1TB disk
that's bad, or the RAID card that is bad.

I seem to see you saying that you think the 1TB drive is actually good?
Did I understand that correctly?

If the 1TB drive is likely good, then are you saying the RAID card is
likely bad?