Operating system: OSX High Sierra 10.13.6
Graphics card: Intel HD Graphics 4000
Short description of error
Blender is not showing Jack in the audio devices list.
Typing bpy.app.build_options.Jack in the python console drops False.
Jack server is properly installed prior to Blender and working fine with other applications.
Exact steps for others to reproduce the error
Under OSX High Sierra 10.13.6 install the latest version of Jack Audio from the official site (JackOSX 0.92_b3). Then install Blender 2.83.3. Although Jack is installed and properly working in other applications, Blender won't detect it and won't show it in the audio devices' list.
When building 2.90 from the source I detected the error. The file jack.h and other jack related files weren't found in the location requested by Blender's installer, because the installer was requesting them in a .../jack/ subfolder. Duplicating Jack files to a .../jack/ subfolder solved the problem. Blender built then correctly and Jack appeared in the devices' list afterwards. Timeline sync using Jack Transport is working as well.
In concrete, I duplicated the files in /Library/Frameworks/Jackmp.framework/Versions/A/Headers/ to the created subfolder /Library/Frameworks/Jackmp.framework/Versions/A/Headers/jack/ to bypass the error. But the former is the folder where Jack installs by default under High Sierra.