I'm just not finding reference to it on the web very easily and I've only seen parts of the movie. Is his mask historically accurate? Was it due to leprosy related deformities? Or something symbolic separate from that?
I know he existed irl but also that much of the film is fictionalized
It's a film thing; in real life, Baldwin did not wear such a mask. I commend to your attention this post just last month re KoH!Baldwin's mask, ably answered by u/EnvironmentalYak217 and u/WelfOnTheShelf.
As always, if anyone else can contribute to the matter, please don't let this post stop you!