Yes, it is actually necessary to derive your own GtkWidget and add the GtkPopover.

Here you can find an example of this:

https://stackoverflow.com/a/78803432/22768315

There is also a reference to further examples.

A more detailed explanation can be found here:

https://discourse.gnome.org/t/gtk4-gtkpopover-finalizing-warning/25881/3?u=holger

Have fun programming in the new year 2025.