If you export the Workspace using the export-fixtures command, it might not work properly. I think you need to create a custom workspace and link it to the module or app. This way, it will be included in your custom app. When you install the application on any site, the workspace will work correctly.
In Website Settings, if you have created a custom theme or used images, you also need to export the submasters of Website Settings. However, for images, you must set them up first, so it’s not recommended to export the Website Settings. You can easily set this up in 2–3 minutes.
Reference of export-fixtures: How to Export Custom created solution to import on another system - #2 by NCP