Please keep me posted on your progress, as I use multiple monitors,
but in Windoze OS and am quite interested. Most of my presentation
laptops for video projectors are equipped, but quite a hassle in MS.

Don;t know how to verify their existence in ubuntulinux, would like to know.
If you have MS installed, you might first verify your present hardware.
Many times they contain second monitor capability just lurking.
It's the ol' "Start / Control Panel / Display / Settings" trail.

I have a dozen computers, some of which had second monitor
capability of which I had not been aware.

At least a first step.