Comment 1 for bug 1819503

Thank you for your bug report, the change was reverted from the ubuntu-settings overide and done in imagemagick itself, that has been removed in disco with the rtaional that imagemagick is not installed by default

https://launchpad.net/ubuntu/+source/imagemagick/8:6.9.10.14+dfsg-7ubuntu1

' * Dropped changes:
    - Stop installing the Debian-specific .desktop for the display program.
      + 'imagemagick' is no longer installed by default for default Ubuntu
        so let's try dropping this change for now.'

You can probably install it, but maybe that should be done automatically on upgrade...