Remap CapsLock to Escape and AltGr to Alt:
setxkbmap -option caps:escape,lv3:ralt_alt
Reset with:
setxkbmap -option
Persistence Link to heading
Set XkbOptions in /etc/X11/xorg.conf.d/00-keyboard.conf:
Section "InputClass"
Identifier "system-keyboard"
MatchIsKeyboard "on"
Option "XkbLayout" "gb"
Option "XkbModel" "pc105"
Option "XkbOptions" "caps:escape,lv3:ralt_alt"
EndSection
Now restart your machine.
Alternative Link to heading
If the above did not work try /etc/default/keyboard:
XKBMODEL="pc105"
XKBLAYOUT="gb"
XKBVARIANT=""
XKBOPTIONS="caps:escape,lv3:ralt_alt"
BACKSPACE="guess"
You can either restart or execute:
sudo udevadm trigger --subsystem-match=input --action=change
Documentation Link to heading
There is none, you can look at these options listed here:
cat /usr/share/X11/xkb/rules/base.lst
Stare at them for a few hours, try some out, and you might stumble upon something useful.