Although my favorite translator is Deepl I have to use it in a browser and sometimes it is nice to have a program especially for the task. This is where Crow translate comes in for me. You can translate using Google, Yandex or Bing just by pasting in one side and watching the translation come out the other.
Hopefully, it will support Deepl in the future.
To install Crow translate on Kubuntu 18.04 go to its home page and navigate to the installation page. It is available for Windows, Pacman, APT or RPM based operating systems. For Kubuntu 18.04 select the apt releases page and then right click and save the latest release which will have a name like crow-translate-2.3.1-amd64.deb. Once that has downloaded, right click on the file and install by choosing open with QApt or Discover package managers. Installation is a matter of selecting the install button and entering your password.