Here's an example web app hello-world in Fennel, parsing requests and responding with HTML rendered from the S expressions: https://gist.github.com/turbo/4388c9ad19028560053951a25b3b45...
While you’re right that there aren’t any docs on working with any of the 3rd party projects listed in the homepage - I found that it was pretty straight forward to use as a drop in Lua replacement by examining the compiled Lua from the online REPL. I was surprised how clean the Lua output is. There is really no magic here. I believe one of the project goals is to stay as close to Lua semantics as possible. Basically just lisp flavored Lua.
In my project I just use the compiled .fnl files as I would any of other .lua file.
Is something specific you’re getting stuck with? I’d be happy to try to point you in the right direction.
It’s really nice! I encourage you to give it another try.