OnPreprocessBuild not called on Mac

I upgraded my project to Unity 2020.3.21f1 (from 2019) and now it seems that all OnPreprocessBuild methods are not being called. It worked before and works on the same project in windows. Any idea what can cause such issue?

 

I seem to recall this subtly changed sometime in the past few years... IIRC you used to be able to just HAVE that method and it would get called, but now I believe you need to implement an interface otherwise nothing happens. Are you implementing the interface?

https://docs.unity3d.com/ScriptReference/Build.IPreprocessBuildWithReport.OnPreprocessBuild.html