I would also be thankful for a bit of work on the documentation! Just reading @kevin.van.rooijen’s addition about configuration helped me understand parts I've struggled with before. What I'm missing with the current documentation is an ordering. When I'm not understanding something, I feel that I've missed something somewhere, and I don't know where to look. If I had an ordered guide to refer to, I could simply continue working down the guide when I need help. Two guides I've enjoyed working with is the https://guide.elm-lang.org/ and the https://shadow-cljs.github.io/docs/UsersGuide.html. Both are ordered (can read from top to bottom) and monolithic (can be read without jumping across to other places). I don't know Duct that well, but I'm happy to read over docs to provide feedback and ask stupid questions.
I wrote a blog post about how to build a service with Duct https://flexiana.com/2020/07/building-web-services-with-duct-1-part it covers just basic stuff, but I could help I guess.