I was always super curious about RxJS and I found it to be super difficult to grasp or to build something more real than console logging a click event or a timer.
That's why I decided to start a small/toy project that uses RxJS + Vanilla JS (Typescript) that does more than just a console.log after a click.
As I said, this is a small project but I tried my best to make it work, it has some nice unit tests written using Jest and some .ts specific stuff (I'm learning Typescript too). The project also has a ToDo list with things some things to address.
That being said, feel free take a look and hopefully it helps you to get a better understanding about how to build something with RxJS.