Keyboard Layout Applet Flags do not differentiate alternate layouts

I’m running Ubuntu-Mate 18.04.

I use the US Dvorak keyboard, but my wife uses the Standard US Qwerty. When I set this up to allow for both keyboards, the keyboard layout applet shows a US flag for both layouts.

I installed dconf-editor to disable the flags and show abbreviations instead, but it shows (en) and (en2) for the layouts. I would like it to show (US) and (DV). This was the default behavior on a Mac system I used to use, and could be configured that way on KDE Plasma.

How do I change these abbreviations in Mate (if possible)?