PCLinuxOS 2019.12 Mate.
I basically got it working in virtualbox. I decided to install it onto real hardware. After updating and rebooting, I got to looking around. I found a virtualbox guest additions icon. But it wasn't in the place the person showed on a youtube video. I need to boot up the live version again in virtual box, just to see if I really missed it, or did it show it after the full install on real hardware?
On real hardware, I'm not sure what I'm doing. The Mate desktop has screen tearing. I don't know how to fix that on PCLinuxOS. I don't even know how to install nvidia drivers on it. I looked around and it appears that some kind of nvidia stuff is installed. But it doesn't make any sense to me. Things look strange. Today I emailed a request to the PCLinuxOS forums. Hopefully they will let me join. Then I'll be able to ask some of these questions there. According to Matt H. It can take up to a week or two before they approve you.
UPDATE 01/03/2020 @ 6:56 pm
PCLinuxOS 2019.12 Mate Live.
Found Guest Addition Icon.
Click on Applications > Software Center > Vbox GuestAdditions Installer
Post Merge: January 03, 2020, 07:47:49 PM
Virtual Box. I tried installing the guest additions before installing. As soon as I rebooted, and logged in. I got full screen!