I've made a bit of progress. a warning to others DONT use Ex2Fsd to try to access Ext partitions in windows. it really messed up my PC, corrupted some files (including some oled images I created) and lied about copying files to the SD card.
I caved and hooked up a monitor to the Pi so I could work out the IP address and SSH in. Now that I've done that I've made some progress.
Here's some things that need fixing.
-the .csv file on the boot partition doesn't do anything. the REAL csv file is in /var/www/html/csv - should probably be removed to avoid confusion
-a bunch of the files in the images folder don't match the names in the csv file
-the fgtjam.bmp file needed to be changed to fghtjam.bmp to be recognized and match the csv (was missing an h)
-taco bell's oled images technically work but because they're not 1-bit most of them are completely illedgible on the OLED.
-a bug or quirk is that the the oled selector doesn't respect the game order of the csv games are always displayed alphabetical by the "rom" name of the csv (the web interface respects the csv order
-another bug is that the oled selector doesn't respect the "enabled" option of the csv games marked as "No" on enabled still appear (the web interface respects this option and will not display games with "No" under the enabled option)
I do wonder if this could be configured to have the dongle, oled, csv, and images mounted to a USB thumb drive that would allow us to mount a 2nd thumb drive to the front and change these parts out as easily as we swap the disc images.
another fun fact is that this image runs well on a Pi2, Pi3, and Pi3B+ you get a minor speed bump with the newer variants. the Pi2 gets to the "Loading Disc" message with in 1 minute 2 second, Pi3 is 59 seconds, and Pi3B+ is 58 seconds. I don't have a Pi4 or 5 to test those speeds, but it's nice I can put some old Pi units to good use here.
Would love to see if this setup can be adapted for other hardware like Konami M2 or Konami 573