The main issue with native dialogs/portals, is that they have reduced feature set, see e.g. [GtkFileChooserNative](https://docs.gtk.org/gtk3/class.FileChooserNative.html). And some might be a problematic trade-off for our use cases. Also note that I can't read anything in the link above about the portals being used outside of a sandboxed app, so I'm not sure if it would happen.