On Gnome, the keyboard layout is presented as the code of the language which is currently selected. In the example below, the English (US) keyboard layout is selected:

I don't know about you, but a country flag there looks nicer to me instead of the language. After this script runs, this is what that would look like for the English (US) keyboard layout:

Ps: Other keyboard layouts/languages are also available

Download it from AUR with yay, for example:

yay -S x11-keyboard-flags

Run it with sudo:

sudo x11-keyboard-flags

Then reset gnome-shell by pressing Alt+F2 and entering the "r" command

And that's it! After these steps you'll see the flags in your keyboard layout selector.

• The flags are emojis copied from getemoji and emojipedia
• The script sets these emojis in the evdev.xml file from X11
• The script makes a backup of the original evdev.xml file before running, if it doesn't exist yet
• The idea for this script was based in this post in Ask Ubuntu.