Ubuntu – Remapping Caps Lock to Escape in Ubuntu 18.04 bionic

I had success using the instructions posted on this blog in a virtual console:

echo -e "$(dumpkeys | grep ^keymaps)\nkeycode 58 = Escape" | sudo loadkeys

I'm not sure how to apply this automatically after every reboot, though.

While researching your question, I also ran across this alternative solution:

You can do the first (mapping Caps Lock to Esc) but you cannot do the second.

Simple Explanation: Caps Lock is just not designed to do something when pressed.

Elaborate Explanation: There are many types of keys. Two of them are Modifier Keys and Lock Keys.

Caps Lock is a Lock Key while keys such as Ctrl, Alt, and Shift are Modifier Keys.

It's apparent from their names that Modifier Keys modify the function of the next key(s) pressed, and Lock Keys act as a toggle switch to turn on or off some particular function.

Now, since Caps Lock is a Lock Key, you cannot have it behave like a Modifier Key without mapping it to one. Caps Lock by itself cannot function as a Modifier Key.