I can’t find anything better than Electron/Tauri for building cross-platform desktop apps.
The browser engine is quite efficient and performant for building complex interfaces
And for what it's worth, Tauri and to a lesser extent Electron is actually quite efficient. It looks bloated as hell because it allocates all kinds of RAM pages it doesn't really use in case it needs to JIT extensively (which usually get compressed or swapped out anyway), but by default it's a decent UI framework.
Tauri takes what, maybe 50MiB of RAM? It's not the most efficient way, but it's as efficient as a usable cross-platform framework gets these days. Electron is four times that, which is still better than the alternative on Linux (which was running the Windows application on Wine before Electron came along).
Telegram is written in native Qt and takes about 1750MiB of RAM on my machine to show me a chat screen. The framework isn't the issue here.