How to change my keyboard layout to carpalx QGMLWB

My operating system is Ubuntu 18.04.3 LTS 64-bit.
My desktop environment is GNOME 3.28.2.

I wish to change my keyboard layout to carpalx QGMLWB, defined on the following webpage.
http://mkweb.bcgsc.ca/carpalx/?full_optimization

Attempt 1: GNOME.

Settings > Language and Region > Input Sources
Dvorak and Colemak layouts are listed, but carpalx QGMLWB is not.

Attempt 2: Sven Hallberg.

I attempted to follow the instructions on the following webpage.
https://www.khjk.org/log/2011/jan/carpalx.html
However, my computer does not have the file /usr/share/X11/xkb/symbols.dir.
As a result, I suspect these instructions are out-of-date.

Attempt 3: X Keyboard Configuration Database.

The webpage that defines carpalx QGMLWB states "Patches to include Carpalx layouts in xkeyboard-config and kbd have been submitted by Perry Thompson."
I have downloaded the most recent version, 2.24, of the X Keyboard Configuration Database from the following webpage.
https://www.freedesktop.org/wiki/Software/XKeyboardConfig
However, being new to Linux, I cannot work out how to use/install/configure it.

What is the best way to change my keyboard layout to carpalx QGMLWB?
If it is by using/installing/configuring the X Keyboard Configuration Database how can I do that?