Is it the true that there is an "official" variant that allow scoring at each end of the turn (instead only at the end of the game)?
If yes, where I can find it?
I haven't heard about it being an official variant. But you can find some tweaks to the scoring rules here and here. I'm not a fan of scoring at the end of each turn - it makes you bookkeeping the scores instead of playing the game (but I like the first idea more). You might get interested in a discussion held here.