Procedure

1. Open the Tweaks application.
2. Navigate into Keyboard & Mouse - Compose Key, and enable it.

3. Choose which key will be used as the Compose key from the listed keys.

   

Procedure

1. Create a local database for machine-wide settings and enter the following:

    # vim /etc/dconf/db/local.d/00-input-sources

   [org/gnome/desktop/input-sources]
   # Set the Right Alt key as the Compose key and enable it
   xkb-options=['compose:ralt']

   If you want to set a different key than right alt, replace ralt with the name of the key as specified in the man xkeyboard-config(7).

2. To override the user’s settings and prevent the user from changing it, create a file /etc/dconf/db/local.d/locks/input-sources and enter the following:

   # vim /etc/dconf/db/local.d/locks/input-sources

   # Lock the list of enabled XKB options
   /org/gnome/desktop/input-sources/xkb-options

3. Update the system databases for changes to take effect:

   # dconf update

4. Users must log out and back in again before the system-wide settings take effect.