Discord isn't really the model to follow here, IMO. They killed their native Android app and moved to React Native, and now they're dropping React Native (while mobile somehow keeps "native UI", according to their CTO's tweet). If they wanted to maximize code reuse and accelerate feature development, they should have instead considered Kotlin Multiplatform, then they could've skipped the React Native detour while actually building apps that are native to the platform. (Rust and its cacophony of UI frameworks are not really platform-native anywhere, as far as I'm aware. Maybe Pop OS, but I don't know anyone targeting that specifically.)
This bit is obviously subjective, but Rust as a language is simply not ergonomic enough for a lot of the use cases people are trying to apply it to, especially UI development. Most of the Rust UI libraries I've seen to date either use a more imperative style, or attempt to replicate more declarative approaches like Compose UI or SwiftUI, but without the nice language aesthetics that make it simple to read and write. And if the counter-argument there is for LLMs to be reading and writing this stuff, that's a whole other can of worms: (1) The subsidized inference era is quickly coming to an end and (2) if you're using LLMs anyway, why not maintain apps that are as native to each platform as possible?