As you may know, Darktable is an open-source photo workflow application and RAW developers, managing digital negatives in a database and allowing the users to view them through a zoomable light table. Also, the users can develop and enhance raw images.
The latest version available is Darktable 2.4.4, which comes with a huge list of changes. For more information, please consult the changelog.
In order to install the software on your Ubuntu 18.04 Bionic Beaver, Ubuntu 16.04 Xenial Xerus or a derivative system, you need to add the PPA, update the local repository index and install the darktable package.
$ sudo add-apt-repository ppa:pmjdebruijn/darktable-release
$ sudo apt-get update
$ sudo apt-get install darktable
Optional, to remove Darktable, do:
$ sudo apt-get remove darktable