How many original plots did Shakespeare actually write?

I read in the introduction of my copy of Othello that the plot was lifted from a story by an Italian called Cinthio, Apparently Shakespeare copied several of his stories, which explains why so many of Shakespeare's plays are set in Italy. I have heard Hamlet was based on a previous play. I am not sure about King Lear. Then there were a lot of histories, based, however tenuously, on real life people and events. Was Macbeth an original plot? I know Macbeth was a real historical figure, but surely he was nothing like the play. I get the impression that plotting was not what Shakespeare was about. He was not interested in writing whodunnits or thrillers. He was more into writing strong human emotion and beautiful language. No doubt he could have invented original plots but he he did not want to waste the time and brain power. Maybe he was always under pressure to get the next play written for the next season.

Love’s Labours Lost and the Merry Wives of Windsor, I believe, were original plots and in the case of LLL not gripping IMHO