gnome-characters from stable does not define any layouts. gnome-characters from candidate and edge do. When refreshing from stable to candidate it fails, but only if the snap has been run.
ken@x230:~$ sudo snap refresh --candidate gnome-characters
error: cannot perform the following tasks:
- Setup snap "gnome-characters" (194) security profiles (cannot setup mount for snap "gnome-characters": cannot update mount namespace of snap "gnome-characters": cannot update preserved namespace of snap "gnome-characters": cannot update snap namespace: cannot create symlink in "/usr/share/X11/xkb/rules/evdev.xml": existing file in the way)
- Setup snap "gnome-characters" (194) security profiles (cannot update mount namespace of snap "gnome-characters": cannot update preserved namespace of snap "gnome-characters": cannot update snap namespace: cannot create symlink in "/usr/share/X11/xkb/rules/evdev.xml": existing file in the way)
This is a known limitation, quoting from https:/
Layouts cannot replace an existing but incompatible filesystem object. This means, for example, that files cannot replace directories or symbolic links, files cannot replace a directory, and existing symbolic links cannot be redirected to a new target. You can, however, replace a directory with another directory.
Having said that, we may be able to lift this limitation. I will consider options and use this bug for tracking.