Mark,
I searched for "input method" but I couldn't find anything relevant (at least not for me).
In Gnome Control Center -> Region & Language
I have two Input Sources: Portuguese (Brazil) and English (US)
In Input Source Options I have "Use the same source for all windows" checked.
In Gnome Control Center -> Devices - > Keyboard -> Keyboard Shortcuts -> Typing
Switch to next input source = Super + Space
Switch to previous input source = Shift + Super + Space
Patrick also suggested the problem was with the input method and mentioned the same issue with Japanese
and that it could be the IM editor activated.
I found 2 INPUT METHOD tools in the menu: Applications -> System Tools ->
The first one (blue icon) opens the uim-pref-gtk.
In the Global Settings there was a check box "Input method toggle" checked with
Input method toggle key set to: "<Meta>space"
I disabled it, but the behavior persisted.
The second tool is the Input Method Configuration (im-config)
It starts with the following text:
"Current configuration for the input method:
* Active configuration: missing (normally missing)
* Normal automatic choice: none (normally ibus or fcitx or uim)
* Override rule: zh_CN,fcitx:zh_TW,fcitx:zh_HK,fcitx:zh_SG,fcitx
* Current override choice: (en_US)
* Current automatic choice: none
* Number of valid choices: 1 (normally 1)
The override rule is defined in /etc/default/im-config.
The configuration set by im-config is activated by re-starting X.
Explicit selection is not required to enable the automatic configuration if the active one is default/auto/cjkv/missing."
And after I went to the steps of configuration selecting the recommendations, it outputs:
"Keeping the user configuration /home/myuser/.xinputrc as missing.
Automatic configuration selects: none
This does not set any IM from im-config.
This is the automatic configuration choice if no required IM packages are installed.
If a daemon program for the previous configuration is re-started by the X session manager, you may need to kill it manually with kill(1).
See im-config(8) and /usr/share/doc/im-config/README.Debian.gz for more.
Everything was working fine 1 week ago.
I could type SHIFT + SPACE and a space character would appear.
I just updated the system.
Thanks in advance.
Regards.