Not strictly Illy, although the files are made using it!
Not urgent, just curious if anyone else is in the same situation and has a better solution.
So I RIP some of my files using Caldera and twice in the last 6 months (both Illy to pdf with placed .ai files that have transparency) the ripped file has lost an element (some part of the placed file), which wasn't caught until after printing.
I can proof print to .tif and sure it's enough to check a file, but it's not ideal - extra rip time plus the default Unix viewer is basic.
Caldera themselves say there is no viewer available for .prt files.
(btw these are not the same as 3D .prt files - the 2013 discussion "Open and view ".PRT" files?" on the Acrobat forum is not relevant unfortunately.)