The Tip Show How-to Add the Darktable PPA Apt Repo for Linux Mint/Ubuntu GNU Desktops.

-
Open a Command Line Console Session
-
Enabling the Darktable Apt PPA
sudo su -c "apt-add-repository ppa:pmjdebruijn/darktable-release"
If Got “User is Not in Sudoers file” then Look: Solution
-
Refresh Apt Repositories
sudo apt-get update