So, you have just installed Ubuntu Linux and have configured a vnc server. Your first attempt at logging in results in an error message similar to: “upgrade vnc server or weaker level of encryption”.
Here is the solution: Install “dconf” (sudo apt-get install dconf”) . Launch “dconf” and search for “require-encryption”. Remove the “check mark” and you should be able to login. I did not have to reboot but ….