Long Story Short: Security issue, Blender doesn't have the rights to open a third party app on MacOS/Linux.

On MacOS/Linux the addon will not launch SP, the addon value is actually not here, this addon is not just for you to not click on SP ^^, however:

Clicking on “Edit with Substance” will still:

• When using Legacy, bake the material ID maps (with applied modifiers if the option is checked), many files will be generated if working with UDIM.
  
• Export all the meshes, part of the current Mix, as an FBX, after applying each modifier and joining every meshes into a unique one, then link that FBX to the project.
  
• Open Substance Painter application => /!\ Not open SP on Mac, you'll have to Click on your app yourself and follow some easy steps* /!\
  
• Create & save a new Substance project named after your Mix name (if it doesn’t exist yet).
  
• Set Substance UDIM project Workflow according to the “Use UDIM Legacy” checkbox (choice only present for 2020.2.0 and upper version).
  
• Set the export textures url to the texture folder (under [MixName] folder).
  
• Import & set correct export preset to work with the synchronisation process.
  

Then “Sync Maps & Create Shaders” functionality will:

• Create a Shader named “pbr_bridge_[MeshName]” (if any material is already assigned)
  
• Populate the shader with the new generated maps
  
• Create a new texture named “pbr_bridge_Disp_[MixName]”
  
• Assign the exported displacement map to that texture
  
• Add a “Subdivision Surface” modifier (with viewport & render level set to 0) to the meshes (if not already present)
  
• Add a “Displacement” modifier to the meshes, using the new “pbr_bridge_Disp_[MixName]” texture (if not already present)
  
• Set the export padding:'Transparent' & dilation:2 for projects using UVTile workflow
  

*So what are these "easy" steps to follow?

In the case of Substance, PBR Bridge Blender addon auto install a Substance addon named "wr-link" when you click on "Edit with Substance".
Sometimes the addon is disabled (it was the case for some users).
So make sure it is enabled like this:

On windows, when you click on "Edit with Substance" the addon is opening Substance with the mesh_filepath as argument.
Once opened, that addon (wr-link) recognizes some PBR Bridge files and then creates a new Substance project with all the right config.

So on Mac, you'll have to mimic the same:

• click on "Edit with Substance"
• open Substance
• create a new project with the exported fbx (cf doc: "Exported material ID maps & FBX can be found in the generated folders next to the blend file at “[BlendFilename] \ [MixName]”")
• you'll see some flickering because the addon will kick in here and create your new project.

The rest is the same as on windows.

The next time you want to edit, just open Substance and the sp project which was generated by wr-link.

In some cases if you changed the mesh, you may have to refresh it manually (cf doc: "The re-importing can be easily done via “Edit > Project Configuration... > Select...”.")

You can ask any question to me or the addon community on my Discord or send me a direct message.