What does Jenkins do that you can't do with GH Actions and Flux?

Based on the last time I looked: good handling of dependencies between builds (e.g. the ability to do an "edge build" where for any change in a given project, you check whether that will break your other projects when they upgrade to depend on that), advanced scheduling, plugins that integrate all sorts of random tools into your build views.

I have been away from Jenkins for a while, that all sounds like stuff I never used, (thanks!)