Not a lot to write about here. But I learned a few things along the way that made my life a little easier and wanted to share them with any other Linux on Acer C720 Chromebook fans.
One of the consequences of ripping Gnome 3 out of my Linux Chromebook and switching to MATE was that I lost the custom keymappings that supported the dedicated Google keys.
By default the special keys on the top row of the Chromebook keyboard between ESC and the Power button are mapped to F1 through F10. To remap these to the pictured functions (mute, volume up, volume down, decrease and increase brightness) I used the mate-keybinding-properties utility.
Mapping mute, volume up and down was easiest, just a matter of finding those commands in the keybinding table and assigning them to F8, F9 and F10.
The brightness controls required custom mappings for the F6 and F7 keys to use the xbacklight command.
For decreasing brightness I put the following text in a custom keymap labeled “Brightness decrease”, closed the dialog, highlighted the new keymap, and then hit the F6 key.
xbacklight -dec 10
For increasing brightness, I added this text to a separate custom keymap labeled “Brightness increase”, closed the dialog, highlighted the new keymap and pressed F7.
xbacklight -inc 10
When it came to getting back the humble “Delete” key, something I’d been missing since putting Linux on the Chromebook, all I had to create another custom keymap to map the Shift+Backspace combination (the key combination used by ChromeOS for deleting a character) to a command containing the following xvkbd command:
xvkbd -xsendevent -text "\[Delete]"
Here’s a good article on installing Debian on the C720 that includes a nice section on keyboard mapping.
This Reddit post has some additional examples of using xbindkeys instead of a gui keymapping tool.