18.04.03 LTS Server Installer does not recognize disk while Desktop Installer does

I was attempting to install Ubuntu Server 18.04.03 to an older machine. I burned the ISO image to a DVD and attempted to install via a USB CD-ROM. The only disk in the machine was a 120GB Seagate IDE disk. In Bios, all settings were set to AHCI and the disk was clearly visible and selectable in the boot-order selection. I had also previously run a check using SeaTools to ensure the driver was OK (SMART OK, short and long test PASSED).

The installer failed to identify any target media for installation. I found no way to overcome this. Things I tried:
- Changing the jumper from Master to CS and varying the position of the drive on the cable
- Wiping the disk of previous (Windows) partitions using gparted from a bootable utility CD
- Playing with various BIOS options (from AHCI to IDE etc)

What I noticed:
- If I used alt-F2 to drop into a shell when faced with the "could not find a media.." message, I ran fdisk -l and the drive was recognized and reported without issue.
- When I attempted to install Ubuntu Desktop 18.04.03, Ubiquity found the drive and installed on it with no problems whatsoever. I changed nothing between my attempt to install Server and my successful installation of Desktop
- After the Desktop installation, I again attempted to install Server. The installer was still unable to find the media.

Is this reasonable or, as I expect, a bug?

I would like to post this as a bug (I didn't see anything similar in LaunchPad), but I don't want to burden the devs if this is somehow expected behavior.

P.