Change:
<del> { lib , stdenv , darwin , fetchFromGitHub , rust , rustPlatform , cargo-tauri , cinny , copyDesktopItems , wrapGAppsHook3 , pkg-config , openssl , dbus , glib , glib-networking , libayatana-appindicator , webkitgtk , makeDesktopItem }: rustPlatform.buildRustPackage rec { pname = "cinny-desktop"; # We have to be using the same version as cinny-web or this isn't going to work. version = "4.0.3"; src = fetchFromGitHub { owner = "cinnyapp"; repo = "cinny-desktop"; rev = "v${version}"; hash = "sha256-05T/2e5+st+vGQuO8lRw6KWz3+Qiqd14dCPvayyz5mo="; }; sourceRoot = "${src.name}/src-tauri"; cargoHash = "sha256-bM+V37PJAob/DA2jy2g69zUY99ZyZBzgO6djadbdiJw="; postPatch = let cinny' = assert lib.assertMsg (cinny.version == version) "cinny.version (${cinny.version}) != cinny-desktop.version (${version})"; cinny; in '' substituteInPlace tauri.conf.json  --replace '"distDir": "../cinny/dist",' '"distDir": "${cinny'}",' substituteInPlace tauri.conf.json  --replace '"cd cinny && npm run build"' '""' '' + lib.optionalString stdenv.hostPlatform.isLinux '' substituteInPlace $cargoDepsCopy/libappindicator-sys-*/src/lib.rs  --replace "libayatana-appindicator3.so.1" "${libayatana-appindicator}/lib/libayatana-appindicator3.so.1" ''; postBuild = lib.optionalString stdenv.hostPlatform.isDarwin '' cargo tauri build --bundles app --target "${rust.envVars.rustHostPlatform}" ''; postInstall = lib.optionalString stdenv.hostPlatform.isLinux '' install -DT icons/128x128@2x.png $out/share/icons/hicolor/256x256@2/apps/cinny.png install -DT icons/128x128.png $out/share/icons/hicolor/128x128/apps/cinny.png install -DT icons/32x32.png $out/share/icons/hicolor/32x32/apps/cinny.png '' + lib.optionalString stdenv.hostPlatform.isDarwin '' mkdir -p "$out/Applications/" cp -r "target/${rust.envVars.rustHostPlatform}/release/bundle/macos/Cinny.app" "$out/Applications/" ln -sf "$out/Applications/Cinny.app/Contents/MacOS/Cinny" "$out/bin/cinny" ''; nativeBuildInputs = [ copyDesktopItems wrapGAppsHook3 pkg-config cargo-tauri ]; buildInputs = [ openssl dbus glib ] ++ lib.optionals stdenv.hostPlatform.isLinux [ glib-networking libayatana-appindicator webkitgtk ] ++ lib.optionals stdenv.hostPlatform.isDarwin [ darwin.DarwinTools darwin.apple_sdk.frameworks.WebKit ]; desktopItems = lib.optionals stdenv.hostPlatform.isLinux [ (makeDesktopItem { name = "cinny"; exec = "cinny"; icon = "cinny"; desktopName = "Cinny"; comment = meta.description; categories = [ "Network" "InstantMessaging" ]; }) ]; meta = { description = "Yet another matrix client for desktop"; homepage = "https://github.com/cinnyapp/cinny-desktop"; maintainers = with lib.maintainers; [ qyriad ]; license = lib.licenses.agpl3Only; platforms = lib.platforms.linux ++ lib.platforms.darwin; mainProgram = "cinny"; }; } </del>

Discussion:
: Fails to load after logging in "Failed to load. WebAssembly.Module doesn't parse at byte 0: module doesn't start with '0asm'" Steps to reproduce the behavior: the package into a Matrix account fails to start with error mentioned before ! <!-- Please @ people who are in the list of the offending package or module. If in doubt, check for whoever last touched something. -- Please run and paste the result. Add a :+1: [reaction] to [issues you find important]. [reaction]: [issues you find important]:
! seems like the wasm file is missing outright for some reason
Fixed by