I've tuned my notification system to work well with a custom desktop environment and I'm handling them internally there, but Ripcord uses a nonstandard way of showing notifications. It would be great if libnotify could be used with the current system as fallback, as it's fairly standard.

No, it doesn't. Ripcord uses Qt, and Qt uses the freedesktop/xdg specification over dbus for tray icons and messages. Something is wrong with your Linux desktop configuration.

See the Qt code that generates notifications

(Though I believe Qt does have some kind of fallback mechanism for notifications... anyway, I can't use libnotify in Ripcord, because it has a bunch of gnome dependencies, and I'm not willing to add those to Ripcord's dependency list.)