Am 25.01.24 um 02:13 schrieb RJ Marquette:
It looks like this is what happened after all. I searched for "MBR Magic aa55" and found someone else with the same issue long ago: https://serverfault.com/questions/580761/is-mdadm-raid-toast ; Looks like his was caused by a RAID configuration option in BIOS. I recall seeing that on mine; I must have activated it by accident when setting the boot drive or something.
I swapped the old motherboard back in, no improvement, so I'm back to the new one. I'm now running testdisk to see if I can repair the partition table.
you learend the hard way *never* add unpartitioned drives to an array
and if it's only to leave 50 MB unused if some clown builds a disk which
is slightly smaller in useable space
