Question: How I should convert a GTK module?

1. I recently read this: https://blog.gtk.org/2018/03/06/input-methods-in-gtk-4/ and I saw an unwanted news for me:

We no longer support general-purpose loadable modules. One of the few remaining users of this facility is libcanberra, and we will look at implementing ‘event sound’ functionality directly in GTK+ instead of relying on a module for it. If you rely on loading GTK+ modules, please come and talk to us about other ways to achieve what you are doing.

So, I want ask you about replicating my appmenu-gtk-module fork (https://github.com/rilian-la-te/vala-panel-appmenu/tree/master/subprojects/appmenu-gtk-module) to new architecture, if I cannot change a general widgets like GtkWindow or GtkMenuBar.

How I can do module like this with new Gtk4 extension points? Or I simply cannot and need to switch to another toolkit?

If I cannot change this architecture, can I port MenuBar -> MenuModel translation in Gtk itself as an option?