I started the gpui-ce fork but I'm becoming somewhat more interested in a fresh framework that is more aligned with the rust ecosystem in general - using crates like glam/glamour, parley, palette, etc
Lots of gpui was built with build Zed/a text editor in mind directly, and as folks have mentioned here, it is hard for Zed Industries to justify work on gpui that is purely for the community. Nathan is usually pretty pragmatic around not optimizing early, and gpui is generally serving Zed's needs at the moment (from what I know, I haven't worked on Zed since July)
I do think ZI would generally benefit if gpui did get pulled out of Zed if there was a community that was passionate about taking it over... but that is time and effort in itself.
You might also want to look into Dioxus Native as it's doing a lot of what you're interested in too, with taffy and vello for example. The gaps I see in the Rust UI ecosystem as you asked are that I want a true cross platform solution for mobile, web, and desktop while most focus only on desktop, as I use Flutter currently for this purpose but need to pull in Rust crates through an FFI layer like flutter_rust_bridge, as well as a backend server in Rust and having to share types with the frontend through some agnostic format like GraphQL, so it'd be nice to have everything in one language. Dioxus Native does in fact bill itself as "Flutter but in Rust" which I'm looking forward to a lot.
How was it like working at Zed? Any reason for leaving?
I would be curious to hear about where folks are finding gaps in the rust ui ecosystem though...
I've written quite a lot of rust UI code for Zed over the past few years so I'm mostly familiar with the pros and cons of gpui, but I haven't spent much time with Iced, Dioxus, Xilem, etc.
Iced is promising, using it for a small side project. Fairly straightforward and easy to use, but lacking basic things from more mature libraries (unsurprisingly, since it's still early). If you want something like a QTreeView for example, you're on your own. It's cool that it supports WASM, though I'd call it alpha support for now.