Enable Function Keys On The Keychron K2 and K3 Mechanical Keyboard Under Linux

Below, you'll find the steps required to create a systemd command that will run at boot to disable the media keys and restore f1-f12 functionality.

Step 1

Open a terminal window and create a new file in the folder
/etc/systemd/system/.
File name should be keychron.service

sudo nvim /etc/systemd/system/keychron.service

Note:

nvim can be exchanged for any editor of your choice for example doom emacs.

Step 2

Paste the following code into the window:

[Unit]
Description=The command to make the Keychron K2-k4 work with Function keys

[Service]
Type=oneshot
ExecStart=/bin/bash -c "sudo echo 1 | sudo tee /sys/module/hid_apple/parameters/fnmode"
ExecStop=/bin/bash -c "sudo echo 0 | sudo tee /sys/module/hid_apple/parameters/fnmode"

[Install]
WantedBy=multi-user.target

To exit nvim press escape then : then w q and enter.

Step 3

In the terminal, in order to enable the service type the following:

sudo systemctl enable keychron

Step 4

To see the changes right away run last command:

sudo systemctl start keychron

Closing Remarks

If you want to simply drag/drop the file that you create manually in the steps provided, I have it under the scripts folder in this repo. Download it and drop it in /etc/systemd/system/, doing Step 3 at the end.