See the commments on this page. The path to the project is converted to Windows one, and therefore the plugin doesn't work correctly on Linux systems.
Specifically one user posted this code:
String defaultPath = projectFolder.getPath().replace("/", "\\") + File.separator + UMLProject.CLASS_DIAGRAMS_FOLDER;
In case you need to find where the output of the error is, here you can find it.
Edit:
This problem is patched in easyUML for Netbeans 8.2, which you can download here. Still, paths don't work well with strange characters such as "°".
See the commments on this page. The path to the project is converted to Windows one, and therefore the plugin doesn't work correctly on Linux systems. Specifically one user posted this code:
String defaultPath = projectFolder.getPath().replace("/", "\\") + File.separator + UMLProject.CLASS_DIAGRAMS_FOLDER;
In case you need to find where the output of the error is, here you can find it.
Edit: This problem is patched in easyUML for Netbeans 8.2, which you can download here. Still, paths don't work well with strange characters such as "°".