Fixing it in LR with the CA tool doesn't really help because it is not really "that" kind of lens CA. All you actually have to do is align those RGB channels. That will neutralize the pseudo CA, and slightly improve sharpness.
- invert the neg,
- basic levels adjustments so I can see something on my screen,
- duplicate the base layer 2 times and turns each layer into a red, green and blue channel
- upscale the image x2 nearest neighbor
- apply unsharp mask on each layer (120% 89 pixels radius here)
The next step is aligning those RGB layers. Here I wish PS had some elastic grid deformation alignment tool... But the auto-align layers function works quite well. I could also do it by hand. When it's done the image can be flattened and I repeat the same process on the 3 remaining scans.
These 4 layers need to be aligned, converted in a smart object, stack mode set to median, and then rasterized. I apply some light smart sharpen on the rasterized output (150%, 4 pixels, remove Gaussian blur, shadows and highlights 50%, 50%, 8 pixels)
To be fair, I had to correct the RGB channels alignments on the original 2400DPI scan, and apply the same topaz denoise filter.
Anyways, as it is, it's easy, and the result is definitely better than the 2400DPI scan.