Some positive progress to report:
- I was writing my install media using rufus in .iso format.
- The QNAP BIOS would not boot that using UEFI. I surmised that this might be a problem.
- I redid the install media using rufus in dd format, and enabled the “fixes for old BIOS” option.
Now the QNAP BIOS will boot the install media using UEFI and the garbled display problem is fixed
Installation is proceeding but it is veeeerrrrryyyy slooooow.
I’m going to ignore it until morning (about 8 hours from now) and, with luck, it will successfully complete overnight.
There’s no M.2 slot in this old QNAP machine. If using the DOM winds up being a performance problem then perhaps I’ll get an inexpensive NVMe SSD and pop that in a USB M.2 carrier that I already have.