A catalog of tutorials written on monads. Feel free to do a PR/raise an issue if you know of any stellar tutorials on it.
Garlandus (2018)
A good tutorial that first introduces group theory and algebraic structures before delving into the details on monads. This way, a somewhat natural progression can be seen on how the ideas got motivated and emerged into Category Theory. The part about duals and natural transformations are well written.
Translation from Haskell to JavaScript of selected portions of the best introduction to monads I’ve ever read
Paul Shen (2020)
Aditya Bargava’s visual introduction to functional programming concepts
Josh Haberman