Edit: Thank you all for the suggestions! It has given me a lot to chew on. I guess I'll start with refining my original question: I am at present trying to browse directories on a hard drive via Ubuntu Studio 20.04, but am unable to read file names in anything but 8.3 format, whereas the original format of naming supports 16 characters.
It has been posited that the additional 8 characters could rely on some process specific to the original equipment (not Ubuntu) to unlock the longer filename, which would be a stopping point of sorts.
I have copied the 42MB drive in this manner [sudo dd if=/dev/sdd of=a path to the USB drive to a file named 42MB.dd I had created beforehand. The 42MB.dd file was written, but I am unable to scrutinize it with testdisk as all I can see are physical drives, not virtual (?) drive images.
I've run into difficulty simply burning the 42MB.dd image onto a CDR. As it is reasonable that if the image can be burnt without losing whatever secret sauce results in 16 character names that I do not need to be able to look at the directory with Ubuntu. That said, I have not exhausted myself yet, so I'll continue to dig away at this from these new and highly helpful angles.
/Edit
Edit part 2: I have not tried disk2file, because their website is disabled; and I have yet to try WinHex as it looks like it's a windows product and I'm wary of adding another layer of potential complication to my process.. but it's not ruled out by a long shot (I have just installed wine).
I have now been able to open the disk image with TestDisk. It appears as if the 8.3 format is baked in from there as well. I did have to "rebuild" the boot sector of the disk image to see this.

I have not yet tried to steer TestDisk onto the original hardware, as I don't want to break anything, yet.
Many thanks for all of the ideas and effort. It may be that I just have to pare 20 years worth of inter-dependent file names down into eight character chunks. Nothing drastic before a few nights of sleep though.
/edit part 2
I have a stack of external SCSI hard drives that have been used with and formatted by an Akai MPC2000 MIDI sequencer/sampler. My aim is to clone these drives into back-up files so I'm no longer relying entirely on old storage.
I have a 42MB drive to start with. When I mount this drive all of the file names appear as 8 character plus extension, whereas the MPC naming convention is 16 characters plus extension. Since a lot of the files are audio samples saved from a particular source, many of the files read as the same name when truncated to 8 characters (and the same file size, which is incorrect - though I believe that will be resolved when file names are complete).
I used dd if="my drive" of="USB thumb" to grab the data. This effectively turned a 16GB USB stick into the spitting image of the 42MB drive - complete with the truncated file names.
I would like to be able to see the data on the drive (or drive clone) complete with 16 character names and accurate files sizes before I archive and move on to the next, larger drive. Any suggestions?