Disable Shotwell on Fedora + Gnome
Found the answer to this conundrum with a little help from the Ubuntu forum but this answer works in Fedora with Gnome, too. Here's my remix of their answer:
To enable or disable automount open a terminal and type dconf-editor followed by the [Enter] key.
Browse to org.gnome.desktop.media-handling. A quick way to do this is to press Ctrl+F (for Find) and then type automount.
The automount key controls whether to automatically mount media. If set to true, then Nautilus will automatically mount media such as user-visible hard disks and removable media on start-up and media insertion. You probably want this on.
There is another key org.gnome.desktop.media-handling.automount-never. By checking this, you will disable Shotwell, and everything else, from running when devices are automounted. So check this to turn Shotwell off.