I am able to remap caps lock to be an extra ctrl key by running the following:
setxkbmap -option "ctrl:nocaps"
However, as discussed in this question, the changes are not persistent (also after any lock, such as suspend). The first answer is not helpful, because I want the change all the time, not necessarily after I've opened a terminal (unless Ubuntu sources .bashrc on login?)
The second answer seems to be what I want, but the referenced
org.gnome.desktop.input-sources doesn't exist for me.
Is there somewhere else in dconf editor (or elsewhere) to set this so it is permanent?