Hey, Its probably a year too late, but I find myself facing the same issue.
Ive been trying for a few days now to get a basic routing with auth set up. I avoided Obelisk because it seemed very opinionated towards nixos and aws for deployments so I took a reflex-platform approach. I finally implemented a basic routing with set up, but now im trying to incorporate the router from the reflex-dom-contrib as it looks to have really nice features.
I also couldnt get reflex-dom-contrib to work as a library, I was thinking about trying to fix the nix package but decided to simply import the code I wanted directly. In the Router.hs most of it worked out of the box with the exception of HasJsContent this is from Foreign.JavaScript.TH .
The api of this library and for this type has changed at least twice since the router.hs in contrib was written first to HasJS and now to JSContextSingleton. Unfortunately its not as easy as just changing the name, Im guessing the Singleton was introduced in an effort of efficiency, tbh I need to do some research and understand the implementation a bit better.
Regardless when I find a fix I will make a PR to contrib but at this stage ive had to change so much I might create a new standalone library with a subset of the essential features that will be easier to maintain into the future.
If anyone comes across this and has an interest please let me know.