Thanks to xrunner, I have made some significant progress (all be it 2 years later).
Copying his instructions (almost verbatim). I got the firmware loader to work. The only difference is that when copying the files on to the local storage, I had to rename it as a .csv rather than a .txt file.
Revisiting the storage and memory situation- I had soldered on two extra NV memory chips bought from Aliexpress, hopefully, they're not full of sand and are functional (well... hopefully they are full of sand... technically...).
Apparently, I had bought a 32MB RAM stick before, but it wasn't in the machine so the only logical explanation is that it evaporated and I will have to get another 32 MB stick.
Now, herein lies the final hurdle. The non volatile SIMM stick has 4 jumpers to indicate the capacity (I assume they aren't the same as EDO ident). So the question remains, how to configure them. I found this on another forum and will attempt to this when the rest of the components arrive:
I restored the flash chips to their original locations, and confirmed
that everything was working as before. Then I ran the flash erase
with several of the other jumper configurations. After finding the
correct jumper configuration, it allowed me to install the latest
firmware, and everything appears to me working well.
If anyone else wants to try this, you need to have both the jumpers
closest to the SIMM's edge connector open, and the other two shorted.
You will have to run the secure flash erase to reformat the SIMM (hold
"view/trace", "ESC", and "return" while turning on the analyzer. The
screen will be blank, but you can tell it's working by checking for
the Vpp voltage of one of the chips. Give it about 10 minutes, and
then pull the plug to turn it off. After erasing the flash, it won't
work until you install the firmware.
Now, the real challenge is if I have the guts to wipe the firmware. I had previously contacted Keysight support (about a year ago) about this and the response I got was, effectively, a very polite middle finger: "No, it's broken (the motherboard), we won't help you, but our new stuff, bye." (paraphrased).