I have Ubuntu 18.04 installed with GNOME.
My left alt key opens application menu while right alt works as expected (left alt + F4 doesn't work for example, right alt + F4 works perfectly).
How can I fix the left alt behavior so that it works like right alt?
The terms we are discussing here are "keyboard shortcuts" and "keybindings". They are useful when searching for help.
First, run xev in a terminal to see if the key works.
If it works, open Settings > Devices > Keyboard for a list of shortcuts. If it says Alt without specifying right or left they should both work. Replace any that specify a side and make sure it only says Alt.
If you have trouble making the settings do that, install dconf-editor
sudo apt install dconf-editor
and launch it from the terminal
dconf-editor
Locate the search icon and type keybinding and look through the paths for what you need. In your example navigate to
org/gnome/desktop/vm/keybindings/close
If the default value is on it should be set to
['<Alt>F4']
If it's not, switch default to off and enter exactly the above as a custom entry.
My Alt shortcuts seem to be the same for each side, so maybe yours got reconfigured somehow.
