I just followed the documentation of the gtk_popover_menu_new_from_model() function and there is a part of its documentation wich refers to a function called:
The documentation is probably not up to date; the function in question is available in the header.
The API reference needs to be updated; currently, the churn is a bit too high to keep track of all changes, but they will be updated before the next snapshot.
In general: check the introspection data to see if a function exists and it’s available. The introspection data always reflects the ABI exposed to clients.