Comment 4 for bug 1906272

It's difficult to say what caused the change in auto mount behavior with your move to XFCE from Gnome. As I understand it, XFCE is not auto mounting the device, and therefore Rapid Photo Downloader does not respond to the insertion. When GIO is running, Rapid Photo Downloader is designed to wait for GIO to automount the inserted device, because that is what GIO is designed to do. This behavior of Rapid Photo Downloader is actually critically important when GIO is running under Gnome. If it does not do this, things break.

As far as I know, while XFCE uses GIO under the hood, it does not develop GIO. Gnome develops GIO. GIO might have changed how it works, and XFCE has yet to catch up. Or maybe XFCE decided not to automount inserted devices anymore. I don't know, which makes it difficult to distinguish between genuine changes in desktop behavior, or actual bugs in GIO / XFCE.