I recently bought a Keychron K2 mechanical keyboard and it’s been great so far. Most things work out of the box on my Linux laptop with a few notable exceptions:

• function keys!
• no insert key!

The issue with function keys:

• when set to Windows mode, the special keys (“volume up”, “brightness control”, etc.) send Windows-specific key combinations instead of standard keycodes that Xorg recognizes.
• when in Mac mode, the Fn key seems useless, there’s no way to enable function keys (to have F12 instead of “volume up”), and the “Command” and “Option” key don’t match the usual order of the Super and Alt keys.

The solution is simple:

• use the keyboard in Mac mode (so that it sends useful keycodes instead of Windows-specific shortcuts)

• configure the Linux hid_apple driver to use function keys and swap “Option” and “Command” by creating /etc/modprobe.d/hid_apple.conf with the following content:

  # For Keychron keyboard -- https://wiki.archlinux.org/index.php/Apple_Keyboard
  options hid_apple fnmode=2 swap_opt_cmd=1
  

You’ll need to reboot (or unplug the keyboard, unload the module, reload it with the correct options, and plug the keyboard), and voilà, it works :)

Now, for the lack of Insert key. I mostly use it in the Shift+Insert combination to paste things from the X primary selection.

The simplest solution I found is to use xmodmap to map Shift+Delete (which I never use) to Shift+Insert. To do that, I created ~/.Xmodmap with the following content:

keycode 119 = Delete Insert Delete Insert

And added this to my ~/.xinitrc:

# Load .Xmodmap if it exists
[[ -f ~/.Xmodmap ]] && xmodmap ~/.Xmodmap

There’s also a list of resources for Keychron K2 Linux users in this Git repo, and on Facebook Keychron created a Keychron Linux User Group.

EDIT: everything in this post also applies to the Keychron K4 keyboard.