I am using Xubuntu 16.04 exclusively on an old MacBook from 2007.
My keyboard is Portuguese. In
Settings/Keyboard/Layout I defined the keyboard model as MacBook,
Change layout option as Left-Alt and
Composer key as Right-Alt. I tried also several 3rd level keys without any luck.
Normally in the Portuguese keyboard I will get the "at sign" symbol using Left-Alt 2.
Now the only way was to do
Ctrl+Shift+U+40 to get the @. I am aware that there are similar questions but with the exception of this answer none have worked.
$ setxkbmap -query -v 10 Setting verbose level to 10 locale is C Trying to load rules file ./rules/evdev... Trying to load rules file /usr/share/X11/xkb/rules/evdev... Success. Applied rules from evdev: rules: evdev model: pc105 layout: pt variant: mac Trying to build keymap using the following components: keycodes: evdev+aliases(qwerty) types: complete compat: complete symbols: pc+pt(mac)+inet(evdev) geometry: pc(pc105) rules: evdev model: pc105 layout: pt variant: mac