The immediate mode Gio (gioui.org) toolkit has support for accessibility (on Android for now), IME and, recently, RTL text layout.
Disclaimer: I'm the author.
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.