As expected, the external 1 TB WD My Book/AV HDD, installed for more than a decade on the now-retired Fios TV DVR, was seen by Windows as a raw disk. I initialized and partitioned it to be used for whatever.
I need to initiate an equipment return process with Verizon, but the drive was my own purchase, so it stays with me. Verizon actually doesn’t care about the old gear, but as I must return the new Fios TV One and Mini, I may as well send the old stuff back as well.