This was my experience as well. Simple windows with a button that increments a number are nice and understandable but if you try to get more complex controls working, you run into docs.

With C code often being unreadable, I found that Vala applications often have readable examples of how to use UI components. However, tooling support for Vala is extremely limited so experimenting with existing code may be a annoying. That said, I've had good experiences with opening these projects in Gnome Builder (once it got updated to work on my computer again).

If your component of choice doesn't have a Vala example, I'd resort to reading the documentation. Reverse engineering the API from the docs is often quite doable if you first look at how a component you do understand.

I've had similar problems, but worse, when I tried mixing Rust and Qt. I've never used Qt before so that doesn't help, but I found the API even less predictable in many cases, with some docs and examples several versions out of date.

I'd seriously consider just shipping a WINE'd Windows binary (using a tool like https://winepak.github.io/) for Linux targets with the current state of Rust GUI platforms. The amount of game UI/custom UI libraries out there is impressive but they all feel terribly wrong when I try to use them, in the same way most Flutter apps are terrible to use on desktop.