The only R34 Rust Lib you need! (Just kidding😜)
With this lil library you can easily generate R34 api urls and parse json responses so you can use them to download content from R34.
There is an example inside the documentation. I hope it's easy to understand.
I made an R34 Downloader that kinda works but has no certificate or anything. https://github.com/NunjaUwU/r34-board-downloader/tree/master