Looks like TL;DW - rewrite Heroic in Rust, and rearchitect it a bit to more easily support other stores than GOG and EGS. There's also an intro to other options.
Eh, I think something like Electron makes a lot of sense, but maybe they'll go with tauri instead if it's going to be written in Rust. The app itself isn't really performance sensitive since it basically just launches games in another process, so using a web view isn't really an issue, and could even be helpful in order to handle 2FA and whatnot.
So I wouldn't expect them to rewrite with GTK+ or Qt or something, but who knows!