The workaround is not pretty. What would work is to open photos with this camera lens combination in another instance of Photolab outside of your lab. The images could be just photos of white walls if for security reasons you can’t take any of the photos out of your lab. Once you have the lens profiles installed in even a trial version of Photolab, those profiles should be able to be moved.
The modules are stored here on Mac:
/Users/~/Library/DxO PhotoLab v4/Modules. There’s a database (SQlite which includes all 74785 lenses) called CAFList4.db. The lens modules themselves have names like C54383b_001.caf (binary) and are about 500KB each. For those who are counting, this would make the full lens database a 37 GB download. The original motivation for not including all lens profiles would have been to save hard drive/SDD space. Of course, now it’s probably to prevent other manufacturers from easily obtaining the full database.
My Modules folder includes 116 .caf files besides the CAFList4.db file. This means that all the lenses I’ve ever had from Photolab 2 on have been moved forward (I do not own 116 lenses but have probably shot with that many, including re-opening older photos). The database appears to look for a local file first and if none is found then offers to download the missing file.
It’s not a bad system but it’s a real nuisance when offline. What is even more frustrating is that it’s not possible to use an existing profile with a non-profiled lens. There’s many manual Pentax and Nikon lenses out there whose optical profile closely matches later chipped lenses but it’s impossible to apply any kind of lens profile to another lens (well it is possible with a carefully built ExifTool command but it’s very fiddly and easy to end up with a bad Exif profile which won’t open a lens profile in Photolab).
Feature request " Option to manually select a lensprofile" has 66 votes!