What is circle at right lower display bezel on CF-19 mk7?

I just got a low mileage CF19 mk7, I upgraded the RAM to 16GB, replaced the 128GB SSD it came with to a 512GB SSD. Boot time is under 10 seconds, and every device driver is installed. Glad I got it. I still have my mk4, I am undecided what to do with it, I might use the 128GB SSD I took out of the mk7 and install Ubuntu on it, is anyone running Ubuntu on a 19?

On the display beze, lower right front of the mk7 is a silver circle approximately 3/8" with a dark circle in the center approximately 1/8".

Anybody know what it is?

 

It's a ambient light sensor.
Yes Ubuntu runs well on cf19 units

 

Thanks.

 

So I have the mk4 running Ubuntu 20.04.

Any direction on how to calibrate the touchscreen and get the tablet buttons working?

I haven't noticed anything else not working, so far......

 

Adventures with Linux: Installing Ubuntu on a Panasonic Toughbook CF-31 - Bob Johnson's Computer Stuff, Inc.

And I'm looking for Panasonic Dashboard for Linux Want to try on my FZ-M1, but can't live without those Dashboard controls