I Observe the following discrepancies between the platforms:

1.) in LinuxAppImageBuilder.copyIcon(), the method AbstractAppImageBuilder.locateResource() is not used to read the icon. This results in the inability to customize the icon resource using --resource-dir on linux, where it can be customized in that way on Mac and Windows platforms (where locateResource() is called.

2.) On Linux, the icons (the main app icon and any icon created from an icon property in an add-launcher property file) are placed in a sub-dir named "resources". On MacOS they are placed in a sub-dir named "Resources", on Windows they are placed in the root of the applications output directory.