Clipboard Managers for Ubuntu as of April 2019

I have been researching clipboard managers for Linux, (Ubuntu with Gnome,) and I am recording my findings here for the benefit of others.

Medium.com: Psychology of Code Readability by Egon Elbre

This is an article I enjoyed reading.  I am in full agreement with every claim made therein. It was very nice to see certain conclusions that I have arrived at in the past being spelled out and illustrated with nice explanations.

https://medium.com/@egonelbre/psychology-of-code-readability-d23b1ff1258a