Maybe I'm overcomplicating things, but what if there was an option to change the keyboard shortcuts? Everything minus Ubuntu could have the defaults be F11=S&F, and Ubuntu could have the default be F11=Fullscreen. I don't have hard numbers, but I'd be willing to bet that a lot of Ubuntu-users are first-time OO.o users, so they're used to F11 being fullscreen. If it bothers older OO.o users, they'll presumably know how to change the settings.
Maybe I'm overcomplicating things, but what if there was an option to change the keyboard shortcuts? Everything minus Ubuntu could have the defaults be F11=S&F, and Ubuntu could have the default be F11=Fullscreen. I don't have hard numbers, but I'd be willing to bet that a lot of Ubuntu-users are first-time OO.o users, so they're used to F11 being fullscreen. If it bothers older OO.o users, they'll presumably know how to change the settings.