I recently upgraded to 20.04, but I know this bug existed in 19.10 and perhaps from the beginning. I enjoy the stock "familiar" Ubuntu Mate layout with the panel on the bottom. I have a laptop display with a 1366x768 screen on a standing desk with an Acer 22" display with 1680x1050 physically mounted above the laptop. I have chosen to have the Acer 22" as my Primary display so this is where all of my Mate panels appear.
- Bug or Issue: when a program is maximized on the Acer 22" display, the bottom Mate panel covers the bottom of the windows. Sometimes this causes the panel to cover up buttons in an application or it covers status information in other applications. This can be seen best in the screenshot below where the bottom status bar of Caja is covered, and where htop in a terminal window you can't see the Fn key commands.
I have tried "hiding the bottom panel" but then it proves difficult to use the functionality of the bottom panel because finding the right spot with the mouse when the displays are stacked vertically to make the bottom panel "unhide" is not easy.