Thanks in advanced
Open it in notepad and you see 'RP Solids -- CSM3.0 Compressed data' - but for the life of me, I can't find anything to work with it. You can't even export it from UPstudio as an STL or 3MF model.
I've tried a few different pieces of software, from 3d Builder to Fusion 360 and Maya. Nothing 'free' opens it as far as I can tell.
You could have a look at some of the stuff that was being done with the original upbox here - https://github.com/UP3D-gcode/UP3D
users developed a method to intercept the USB data and convert it to gcode - if you can reimport the gcode and convert it to a model you might be able to get somewhere.