Thanks!
I wouldn’t reccomend doing that in this case – as it will apply to all modules (and that’s why you’re getting the funky paths).
If you have a pom.xml for the /frontend/ directory (I think when you say They are declared in the root pom.xml that means yes), you can adjust sonar.sources specifically for that module.
<properties>
<sonar.sources>component</sonar.sources>
</properties>