The first thing you must do is to edit your xorg.conf file to accept a ‘virtual’ resolution. Then you will make use of the cvt and xrandr commands to establish the capabilities of your monitor and finally to obtain your desired resolution. Find all the details here. It’s a good guide but a little confusing in that the first things you need to do are documented toward the end of the article.

Hopefully, you will soon be looking at the display that you desire. The next time you boot it will be gone and the procedure must be repeated. This is corrected by writing a shell script and making it execute at boot time. The details are here. There is an omission in this article. It fails to give an example of the first line of the shell script. For most people it will be “#!/bin/sh”.

Comment: As long as the Ubuntu crew allows bugs like this to get by, it will remain a “geek’s” OS. While the instructions are not too bad, I cannot imagine a “non-geek” locating the fix, editing the configuration files and composing a shell script. I have the time but many others will not.