CAD, CAM, EDA, audio/video production (NLVEs, DAWs, synthesisers etc.).
There are open source options sometimes, but they are all faaar behind the commercial options. No fiscally sane business or government department would use them (unless they only need a small job, or are quite masochistic).
Lol surely Linux can't have a CoC or Linus would be out in seconds? I wonder if he gets an explicit exemption.