I still have a copy of the last Last Fucklord (TLLF?) version. It's pretty much the same aside from what's been said already.
SL has mentioned before that most major aspects of the story and characters were planned from the start. Changing the name feels like a big deal, but settling on the name for a work can be quite difficult, and "Sovereign" felt more appropriate for how serious the story would become. At the time, fans were rather split on the rename (though no one was angry or anything) but I think if you polled the fandom today there would be consensus that "Fucklord" is a bit silly for the game's overall tone. And it would be even more surprising to players if a game with "Fucklord" in the title became a spreadsheet simulator rather than a light-hearted sex romp, maybe not surprising in a good way.