Lumo Desktop

An unofficial Linux desktop wrapper around Proton's Lumo web app, packaged as a single Flatpak that runs on any distro.

Unofficial. This project is not affiliated with, endorsed by, or supported by Proton AG. "Lumo" and "Proton" are trademarks of Proton AG, used here only to describe what the app connects to. The app loads Proton's web app unmodified — no reimplementation, no scraping. The app icon is Proton's own Lumo mascot artwork, reproduced from lumo.proton.me so the app is recognisable next to the web app, and it remains Proton AG's property. If Proton asks, this project will rename and change its icon.

More screenshots

Contents

• What it is
• Features
• Install
  • From a release
  • From source
• Uninstall
• Usage
  • Show/Hide toggle
  • Tray icon
  • Keyboard shortcuts
  • Where links open
• Privacy & security
• Updating
• Troubleshooting / FAQ
• Development
  • Repo layout
  • Design rules for contributors
  • Releasing
• Status & limitations
• Contributing
• License
• Acknowledgements

What it is

Lumo Desktop is a thin Electron shell around lumo.proton.me. It doesn't reimplement Lumo's API or protocol, and it doesn't touch login, 2FA, or encryption — Proton's own unmodified web code handles all of that, running inside the wrapper exactly as it would in a browser tab. What the wrapper adds is native desktop integration: a window, a tray icon, keyboard shortcuts, spellcheck, notifications, and portal-based file dialogs, packaged once as a Flatpak so it runs the same way on any Linux distro instead of chasing per-distro builds.

Features

• System tray icon with a quick show/hide toggle.
• Show/Hide from anywhere via flatpak run io.github.davethegamedev.LumoDesktop --toggle, bindable to a global keyboard shortcut.
• Native desktop notifications.
• Spellcheck with right-click suggestions (Electron's built-in spellchecker).
• Portal-based file dialogs — uploads and downloads go through the XDG desktop portals, not broad filesystem access.
• Wayland native, with an X11 fallback.
• A handful of keyboard shortcuts for navigation and zoom (see Usage).
• Links to other websites, and to proton.me pages other than Lumo/account, open in your default browser instead of inside the app window.
• No telemetry, no crash reporting, no update checks.

Install

From a release

Download LumoDesktop.flatpak from the GitHub Releases page, then install it either way below. The runtime (org.freedesktop.Platform//25.08) and org.electronjs.Electron2.BaseApp are pulled from Flathub automatically, so the Flathub remote has to be configured first. Most distributions ship it enabled; if not, add it with:

flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo

With your distribution's software centre

If your desktop has a software installer that handles Flatpak (GNOME Software on Fedora and Ubuntu, Discover on KDE, and others), open the downloaded LumoDesktop.flatpak with it, for example by clicking it in your browser's downloads list or double-clicking the file:

If asked which app to open it with, pick your software centre (here "Software Install", which is GNOME Software):

Then press Install. If the installer offers a choice between a plain install and one marked User, pick User. It installs for your account only, needs no administrator password, and matches everything else in this README.

From the command line

flatpak install --user LumoDesktop.flatpak

Launching

Start it from your app grid ("Lumo Desktop") or with:

flatpak run io.github.davethegamedev.LumoDesktop

From source

Prerequisites:

• Node.js >= 22
• Flatpak, with the build tools installed:

  flatpak install --user flathub org.electronjs.Electron2.BaseApp//25.08 org.flatpak.Builder

Build everything (packages the Electron app, then builds and installs the Flatpak):

scripts/build-flatpak.sh

This produces LumoDesktop.flatpak in the repo root and also installs the app to your user Flatpak install. Pass --no-bundle to build and install locally without producing the .flatpak bundle file.

Uninstall

Remove the app, keeping your login and settings in case you reinstall later:

flatpak uninstall --user io.github.davethegamedev.LumoDesktop

Or use your software centre: find "Lumo Desktop" in its installed apps and press Uninstall.

To also delete the browser profile (cookies, session, window state), run this instead:

flatpak uninstall --user --delete-data io.github.davethegamedev.LumoDesktop

Then clean up anything left behind:

• Any flatpak override you set for the app (from Privacy & security or Troubleshooting):

  flatpak override --user --reset io.github.davethegamedev.LumoDesktop

• The keyboard shortcut for the --toggle command, if you added one in GNOME or KDE settings.
• The shared runtime and Electron base app, if nothing else uses them:

  flatpak uninstall --user --unused

If you ran the app from source with npm start, its profile lives at ~/.config/Lumo Desktop/ and is not touched by any of the above; delete it by hand.

Usage

Show/Hide toggle

Bring the window to the front (or hide it) from anywhere, without clicking the tray icon:

flatpak run io.github.davethegamedev.LumoDesktop --toggle

Bind this to a keyboard shortcut:

• GNOME: Settings → Keyboard → View and Customize Shortcuts → Custom Shortcuts → Add Shortcut, using the command above.
• KDE Plasma: System Settings → Keyboard → Shortcuts → Add New → Command or Script, using the command above.

Tray icon

Vanilla GNOME Shell doesn't render StatusNotifierItem tray icons without the AppIndicator and KStatusNotifierItem Support extension. The app is fully usable without a tray icon — use the --toggle command above, or relaunch it.

Keyboard shortcuts

Shortcut	Action
Ctrl+Q	Quit
Ctrl+W	Close to tray
Ctrl+R	Reload
Alt+Left / Alt+Right	Back / forward
Ctrl+Shift+H	Back to Lumo home
Ctrl+Plus / Ctrl+Minus / Ctrl+0	Zoom in / out / reset
Alt	Show the menu bar
Ctrl+Shift+L	Global show/hide (X11 only — see Troubleshooting)

Where links open

Only lumo.proton.me and account.proton.me can take over the app window. Popups that Proton's pages open with window.open() (for example during sign-in) get their own sandboxed child window as long as they stay on proton.me. Every other proton.me page, and any external link, opens in your system's default browser instead.

Privacy & security

• The renderer runs with contextIsolation on, sandbox on, and nodeIntegration off. The preload script exposes nothing to the page, and there is no IPC between the page and the main process.
• The main process never reads cookies, intercepts requests, injects scripts into the page, or overrides certificates. It only handles window/tray/shortcut plumbing and a navigation allowlist.
• Login, 2FA, SRP, and end-to-end encryption are entirely Proton's unmodified web code — this wrapper never touches credentials or cryptographic material.

Flatpak sandbox permissions and why each is needed:

Permission	Why
--share=ipc	X11 shared memory (MIT-SHM); needed for acceptable rendering performance under X11
--share=network	Reach lumo.proton.me / account.proton.me and download spellcheck dictionaries
--socket=wayland	Native Wayland windowing
--socket=fallback-x11	X11 fallback for non-Wayland sessions
--device=dri	GPU acceleration for rendering
--socket=pulseaudio	Audio and microphone, so Lumo's voice input can work
--talk-name=org.freedesktop.Notifications	Native desktop notifications
--talk-name=org.kde.StatusNotifierWatcher	System tray icon (StatusNotifierItem protocol)
--env=XCURSOR_PATH=…	Cosmetic — correct cursor theme inside the sandbox instead of the X11 default

Deliberately absent: no --filesystem permission (file uploads/downloads go through the XDG portals instead of direct filesystem access), and no access to the keyring (org.freedesktop.secrets) — the Secret Service API has no per-app isolation, so granting it would expose your entire keyring to the app for very little gain (see SECURITY.md).

Data location: the browser profile (cookies, session, window state) lives at ~/.var/app/io.github.davethegamedev.LumoDesktop/config/Lumo Desktop/ when running as a Flatpak, or ~/.config/Lumo Desktop/ when run via npm start. Deleting that directory logs you out and resets the app.

Cookies are stored in plaintext by Chromium, because the keyring is not reachable inside the sandbox. Rely on full-disk encryption to protect them at rest.

Spellcheck dictionaries download from Google's CDN the first time each language is used, which reveals your IP address and locale to Google. Typed text itself stays local and is never sent anywhere except to Lumo/Proton as part of your conversation.

No telemetry, no crash reporting, and no update checks are performed by the wrapper itself.

To revoke audio/microphone access on an installed app without rebuilding:

flatpak override --user --nosocket=pulseaudio io.github.davethegamedev.LumoDesktop

Undo with:

flatpak override --user --socket=pulseaudio io.github.davethegamedev.LumoDesktop

See SECURITY.md for the full security model and how to report a vulnerability.

Updating

The app has no auto-update mechanism and is not on Flathub, so updates are not offered by flatpak update or your software centre. New versions are published on this project's GitHub Releases page; use the Watch → Custom → Releases option on the repository to get notified about them.

To update, download the new LumoDesktop.flatpak and install it the same way as the first time (see Install):

flatpak install --user LumoDesktop.flatpak

This replaces the installed version in place. Your login, settings, and any flatpak override you set are kept. Quit the app first (Ctrl+Q, or from the tray icon) so the new version is used on the next launch.

Updating matters for security: the app bundles Electron, which bundles Chromium, and neither is updated by anything other than a new release of Lumo Desktop. If you build from source, bump the electron version in package.json and rebuild with scripts/build-flatpak.sh to pick up Chromium fixes yourself.

Troubleshooting / FAQ

No tray icon on GNOME. Install the AppIndicator and KStatusNotifierItem Support extension, or just use the --toggle command / relaunch the app — the tray icon is not required.

"Can't reach Lumo." The window shows this page with a Retry link when Lumo can't be reached. Check your network connection and retry.

The window won't come back after closing. Closing the window (the X button or Ctrl+W) hides it rather than quitting. Run flatpak run io.github.davethegamedev.LumoDesktop --toggle, or relaunch the app.

The global shortcut (Ctrl+Shift+L) doesn't do anything. Electron's globalShortcut only works reliably on X11. Under Wayland, use the --toggle command with a compositor-level custom shortcut instead (see Usage).

The window buttons (minimise / maximise / close) are barely visible, or the title bar doesn't match my GTK theme. GNOME's Wayland compositor doesn't draw window frames, so Chromium draws the title bar itself from the GTK theme inside the sandbox — and some themes get their Chromium-specific rules wrong (Breeze's dark variant, for one, paints dark buttons on a dark bar). The launcher therefore pins the frame to GTK's built-in Adwaita theme, light or dark following your system colour scheme at launch; switching light/dark while the app is running takes effect after a relaunch. To use your own theme anyway:

flatpak override --user --env=GTK_THEME=Breeze:dark io.github.davethegamedev.LumoDesktop

Undo with flatpak override --user --unset-env=GTK_THEME io.github.davethegamedev.LumoDesktop. When running from source with npm start, the pin isn't applied — set GTK_THEME=Adwaita:dark (or Adwaita) in the environment yourself if you hit the same problem.

I want to fully reset the app. Delete the profile directory (see Privacy & security for the path). This logs you out and clears all local state.

Login trouble. The login page is Proton's own code, unmodified by this wrapper. If you're having trouble signing in, first try logging in to lumo.proton.me in a regular browser to rule out an account-side issue.

"Unsupported browser" wall. If Proton ever shows this, please open an issue — there's a user-agent override in src/main.js that can be enabled to work around it.

Development

npm install
npm start

Enable debug logging with:

LUMO_DESKTOP_DEBUG=1 npm start

Repo layout

• src/main.js — Electron main process: window, tray, shortcuts, navigation allowlist.
• src/preload.js — deliberately empty preload script; see the comment at the top for why.
• flatpak/ — the Flatpak manifest, desktop entry, and metainfo.
• scripts/ — build tooling (build-flatpak.sh).
• docs/RESEARCH.md — research notes from before this project started.

Design rules for contributors

• No preload bridge / contextBridge API. The renderer gets nothing from Node or Electron; keep it that way.
• The navigation allowlist (only lumo.proton.me and account.proton.me render in-window; other links open externally) stays as-is.
• Don't add new sandbox permissions unless there's no portal-based way to do it. Prefer XDG portals over --filesystem or other broad grants.

Releasing

1. Bump version in package.json and add a matching <release> entry to flatpak/io.github.davethegamedev.LumoDesktop.metainfo.xml.
2. Run scripts/build-flatpak.sh to produce LumoDesktop.flatpak.
3. Create the release:

   gh release create vX.Y.Z LumoDesktop.flatpak --generate-notes

4. Publish the checksum in the release notes:

   sha256sum LumoDesktop.flatpak

Status & limitations

• Version 0.1.x — early days, tested on Fedora / GNOME Wayland only so far. Reports from other distributions and desktops are welcome.
• Not on Flathub, and not planned unless the app is renamed — Flathub's naming/branding policy doesn't allow a Proton-derived name for a third-party wrapper like this.
• No auto-update mechanism.
• Tray icon requires a GNOME extension (see Usage).
• The global keyboard shortcut only works on X11; use the --toggle command under Wayland.
• The window frame (title bar and its buttons) always uses GTK's Adwaita theme, in the light or dark variant picked at launch — see Troubleshooting.

Contributing

Issues and pull requests are welcome. Please keep the wrapper thin (see Design rules for contributors above), and test changes both with npm start and with a full Flatpak build (scripts/build-flatpak.sh).

License

GPL-3.0-or-later. Copyright (C) 2026 DaveTheGameDev. See LICENSE for the full text. Electron and Chromium ship their own licenses inside the bundle.

The app icon (assets/icon.svg and assets/icon.png) is Proton AG's Lumo mascot artwork, reproduced from the SVG favicon served by lumo.proton.me. It is Proton's property and is not covered by the GPL. Anyone forking this project for something other than a Lumo client should replace it.

Acknowledgements

• Proton for Lumo, the web app this project wraps, and for the Lumo mascot artwork used as the app icon.
• Electron.
• Flathub's Electron2 BaseApp and zypak, which make sandboxed Electron on Flatpak possible.
• kenvandine/proton-lumo-ai, studied as prior art (a Snap-based Electron wrapper); no code was copied.