Desktop app. Download an installer from Releases:

• Windows: the -x64.exe for most PCs (Intel and AMD), the -arm64.exe for ARM PCs (such as Snapdragon). It installs into Program Files, adds ILLUMinator to the Start menu, and the last page of the installer has a checkbox to put a shortcut on the desktop.
• macOS: the -arm64.dmg for Apple Silicon, the -x64.dmg for Intel. The app is not code signed: right-click it and choose Open the first time.
• Linux: the .deb for Debian and Ubuntu (sudo apt install ./ILLUMinator-*.deb), or the .AppImage for other distributions (chmod +x it, then run it). The .deb adds ILLUMinator to the applications menu. The first time an AppImage runs it asks whether to add itself to the applications menu, with a checkbox for a desktop shortcut; it only writes into your home folder.

Or run it from source (Node.js 20 or newer):

git clone https://github.com/AbstractPolygon/ILLUMinator.git
cd ILLUMinator
npm install
npm start

npm run dist builds an installer for your system (Windows, macOS, Linux).

Browser. Each release also has the web version, ILLUMinator-<version>-web.zip: unzip it and upload what is inside to any web server (served over HTTPS). Or serve the app folder of the source; nothing to install for the people who use it.

npm run web            # http://localhost:8080
npm run build:web      # a static copy in dist/web, for any web server

ILLUMinator needs a browser with WebGL 2 for fast rendering (any current Chrome, Edge, Firefox or Safari). Without it, everything still works on the CPU, more slowly.

• Drag .LFR / .LFP files anywhere onto the window.
• Settings → Import Lytro Desktop library… for your old Lytro Desktop library.

Every photo you open is added to your library, so it is there next time (Library and Albums).

• Left sidebar: the library: All photos, your albums and the photos in the selected album. Choosing an album shows its photos as a grid of thumbnails in the middle; click a photo to open it.
• Middle: the picture. Click to focus on that spot; drag to move the viewpoint. Above it, and switch between the picture and the raw microlens image, with the zoom controls on the right; below it, the animation controls.
• Right sidebar: the editing panels (Editing). Click a title to open or close it.
• Top bar, right:

Full screen (click again or press Esc to leave)

About

Settings

Every change is saved with the photo as you make it; there is no Save button. Open the photo again and it looks as you left it. Reset buttons and double-clicking a slider put things back.

The desktop app checks for a newer version when it starts. If there is one, a popup lists that release's downloads (Windows, macOS and Linux, with this computer's first), each a direct link to the file. Install it over the current version; your library and edits stay as they are. Don't remind me about this version skips that release.