Ubuntu 20.04
FG 19.1.1 it is what is now in the archives.
I somehow turned on stereo mode and can't find a way to turn it off.
Ha! I figgered it out myself.
I guess I will put the answer here in case someone else needs it.
I was not able to turn it off because the check boxes and pulldown menus would not work.
It seems that the graphics display is not registered correctly in the horizontal direction so that the cursor must be moved way to the right of the target area to get a response to the mouse click.
You see two dialog windows in the twin displays and you have to pretend that there is only one window and it is really in the middle even thought they appear to the left and the right.
By experimenting and clicking somewhat in between the two windows you finally get the response you wish.
I hope this is understandable.
So by doing this I was able to pull down the menu and select OFF.
Then you must click the close button at the bottom (not the X at the top right) to save the new setting.
You can probably guess how I know that - I had to got through the guessing and pecking procedure more than once.