Edit: replying to https://tritium.legal/blog/desktop, not the OP
AFAIK people 100% are using other libraries for UI, but often use a macro or something to force Rust to behave in a way that those libraries expect.
I haven't read about this in literally years, but that's my recollection.
Also, we don't have good cross platform desktop GUI libraries in C. That's why everyone started using Electron.
(*) with some small exceptions
I find it odd the broader hacker community feels the need to requestion and cross-examine every choice for using rust. Like, no other language has such great just works ergonomics, with a solid language, fantastic tooling, excellent packages that gives it a just works the first time cross-platform joy. Why does every thread have to spawn a brand new unsupported whinge throwing dirt at what seems like such an obvious enjoyable choice?
Also the company seems to be trying to wiggle out from under the open source spirit of the license the last few years, which doesn't bode well.
Then there is the issue that the Rust community likes to rewrite classic C programs because of "memory safety" and "modern tooling," but really just focuses on the easy 80% of the work. It feels like these rewrites are more done to gain popularity on GitHub than anything, as they most often remain incomplete and never replace the original implementation.
Finally there is the GPL to MIT licensing issue, on which much has been said already.