Where to put xmodmap command execution for remapping CapsLock to Esc?
Solution 1:
The problem is that xmodmap is deprecated, and the keyboard layout is resetted at strange times. See if https://askubuntu.com/a/464618/16395 can help you.
In gnome-shell you can achieve this thing by setting, in gnome-tweak-tool, one of these options:
You should be able to find an equivalent thing for Elementary.
See also https://askubuntu.com/a/629043/16395 and Map AltGr-[a..z] and Shift-AltGr-[A..Z] to greek letter