Theoretically, this might work...

sudo gainroot
apt-get -f install

... or if it doesn't...

sudo gainroot
cd /var/lib/dpkg/info
mv freeciv-*post* /tmp
apt-get remove freeciv-client-sdl freeciv-data freeciv-server

... but it might not, too, and might break things more. (Not a confident disclaimer, but I'd seriously wait for someone else who knows more about debian packaging to chime in.)

That's great news! But I think the best solution is going to be to have a task switcher button there anyway; I have hqh's camkeyd installed, but most people are going to need a software key to switch out, and that's the best place for it for consistency.

And/or a fullscreen toggle button in the bottom right, but the old always fullscreen behavior with a task switcher button would be a much easier way to work around the too-tall dialogs issue.