Just to clarify things.
First of all, you should know that a .love file is just a zipped folder, and that's why you can "execute" a folder like that.
Now, let's assume your
main.lua is in a folder called
mygame, in your desktop. That makes it a love folder, which you can open with LÖVE as if it were a .love file.
Now there's two ways of doing it. The first is to do it in a single shot:
The tilde is a shorthand for
/home/yourusername. I'm assuming that your Ubuntu is in English (cause the Desktop can receive other names in other languages). Also pay attention that Linux is case-sensitive, so it won't work if you type
desktop instead of
Desktop. But you get it, that command runs that folder with love.
But there's a slightly different way. First, you go to that folder:
cd means "change directory".
And once you're there:
The dot means "this folder I'm in".
I don't hang much around these forums nowadays, but you can PM me if you need any Ubuntu-specific help.
EDIT: Oops, seems I was a bit late. Or maybe I didn't read the whole thread, sorry. Anyway... can you try installing löve again? Maybe from the command line with:
Also, are installing from Ubuntu's repos, or from löve's PPA? Cause the first one might be outdated.