I use i3wm, and to map cap lock to escape, I run:
setxkbmap -option caps:swapescape
This works fine, but sometimes while hitting the F1 key, my pinky can accidentally hit the Escape key, which turns on CapsLock.
Gnome has a very nice way to do this, where Shift + Escape = CapsLock. Hitting Escape on its own will do nothing.
I use keyd for software remapping now, and I like it a lot more than xkb’s esoteric options. It has functionality for layers like layer:C, where any “passthrough” input will have the defined modifier (or combo like C-S-M), but you can define whatever other bindings inside.
Long story short, I’ve used it to remap caps, control, shift (with a custom shift layer for some symbols), and meta, with overloads, double tap/hold into layers, oneshots, timeouts, and all sorts of (surprisingly fluid) nonsense. It’s so much easier than wading through xkb options for me.
To sidestep the question slightly less, I always got rid of capslock altogether instead of swapping. That still leaves true escape to be hit accidentally, but I think there should be an option to change escape too?
Edit: what I always used was
# make CapsLock behave like Ctrl: setxkbmap -option ctrl:nocaps # make short-pressed Ctrl behave like Escape: xcape -e 'Control_L=Escape'
from here