The answer is moderately involved. The crux of it is: "Automount has always been disabled in BitCurator, but the behavior when clicking on disk images in Ubuntu has changed between 16.04 and 18.04. There is a way to enforce either behavior in 18.04 (BitCurator 2.0.6) but it involves a compromise." Read on for the full answer.
In the BitCurator 1.8.x (based on Ubuntu 16.04LTS) track, the default behavior for Ubuntu when you double-clicked on a disk image was to mount it - whether or not the "automount" behavior for the relevant GNOME component had been disabled (which it *was* in BitCurator). In the BitCurator 2.x.x (based on Ubuntu 18.04LTS, where Unity has been dropped and full GNOME is now used) track, the default behavior for Ubuntu when you double-click on a disk image is to mount it if you have automount enabled, and to do nothing if it is disabled (which it *is* in BitCurator). So what you're seeing is a change in the underlying behavior of Ubuntu. BitCurator prefers safety, so automount is always disabled to ensure physical devices are not mounted when plugged in; but in Ubuntu 18.04LTS this means double-clicking on a disk image will no longer mount it.
There are two ways to navigate this in normal operations in BitCurator 2.x.x: (1) You can use the right-click context menu and go to "Scripts->Disk Image Mount" to mount your disk image (similar to how this script worked in BitCurator 1.8.x). Or if this doesn't work for you for some reason, (2) you can re-enable automount by doing the following:
a. Click on the "Show Applications" grid in the bottom left of the screen.
b. Type "dconf" in the search bar, and start the dconf editor by clicking on it
c. Dismiss the "You might break everything be careful" dialog
d. Navigate to org->gnome->desktop->media-handling
e. Re-enable automount by clicking the appropriate slider
You can now double-click on disk images and see them automount. However, any physical device you plug in *will also be automounted*. As far as I am aware, there's no simple way to do one but not the other.
Kam