FWIW, Gio (gioui.org) recently added support for RTL languages and complex scripts. So there's no fundamental reason immediate mode UIs can't have the nice features you're used to from retained mode UIs.
I can also report some modest progress on my own work on accessibility of immediate-mode GUIs. I have a branch of the Rust egui library [1] that has basic accessibility on Windows using my AccessKit project [2]. I do have a long way to go to make this fully usable and ready to submit upstream, especially when taking non-Windows platforms into account.
Sadly even imgui cannot get around the fact that many operating systems (macOS/iOS/Android) force you to give up your main thread. Linux and, perhaps surprisingly, Windows are good guys in this regard.
It happened by accident. Originally I wanted to run on bare-metal, and thought UEFI would be a good starting point. THen I never got around to adding multiboot and similar support.
Gomobile bridges Java and ObjectiveC/Swift to Go, and probably entails the same overhead the author is trying to avoid.
Shameless plug: If you like Go and immediate mode UIs in particular, Gio[0] runs the same Go code across desktop and mobile alike. No bridging or native code required.
If you like a more mature framework and don't mind Dart, I think Flutter is an attractive toolkit. I started Gio wanting to write a Flutter clone in Go before going for the immediate mode design.
