3rd level key options hidden in Tweaks if show-all-sources is true

[Gunnar Hjalmarsson]

Steps to reproduce:

* Enable show-all-sources

  gsettings set org.gnome.desktop.input-sources show-all-sources 'true'

* Open Tweaks and navigate to Keyboard & Mouse ->
  Additional Layout Options -> Key to choose the 3rd level

* Find that only two odd options are shown

I would have expected the lv3:* options to be shown, i.e.:

  grep lv3 /usr/share/X11/xkb/rules/base.lst

If I downgrade xkb-data to 2.26-2ubuntu4, the issue is not present. So the issue seems to be caused by some kind of incompatibility between gnome-tweaks and xkb-data 2.29-2.

[Gunnar Hjalmarsson (gunnarhj)]

Originally reported at <https://askubuntu.com/q/1297531>.