Today I learned that you can have an installation of Visual Studio 2017 without the JIT debugger - Yup, you really can. This meant that I could not use the technique of attaching a debugger at runtime using the System.Diagnostics.Debugger.Launch(); code snippet.
When the application executes the launch code, nothing happens - no error nor exception. The method even returns true indicating a a successful launch.
After equal parts of scouring the web and pulling my hair out, I eventually stumbled upon the following option in the Visual Studio setup:
The combination of features selected had somehow unchecked the Just-In-Time debugger. Heck, I didn't even know you could not install it. I hope this helps someone else out there.