You are completely right that FP is lacking in guides that go beyond the basics. There's a great abundance of introductory material, but very little about how functional programmers structure large programs or deal with complex I/O.

That is way too much for me to put into a single comment, but the most common approach is to split your program into "pure" and "impure" parts and then model all of your interactions with the real world in a way where the "pure" part of your program becomes an "interpreter" that deals with the pure representations of real-world events.

A common pattern for doing this (but by no means the only one) is using Free Monads.