You basically preempted nearly every single option, including an incumbent one. I don't believe it's fair to judge Rust based on its compatibility with Qt alone - something written in C++. Nothing against C++, but it's harder to get C++ and Rust to work together. You haven't addressed Iced yet, though going by your requirements, you're unlikely to be satisfied by it as well. Iced is not there yet, but it is the native GUI toolkit of the Cosmic desktop.