well its not just for lore you also get a bike for getting all of them which is reason why most people are gathering field notes atm,
I don't think you can get "Fortunate" with duels you need preparation and correct set up to beat them especially Lyon.

the Stars on the cards determined the rarity Lyon is 5 star so his notes either require a lucky drop or win the duel which requires effort and it can drop from Castrum it took me 47 castrums but it dropped for me.