Desktop app is not going away, and offline support is not going away. It now has data browsing built in (that will only work when online), but local files and websockets will still work fine offline. The desktop app does prompt for sign in the first time you open it, but after that you can be offline.
Integrated UI simply means that the old “data platform” UI and “studio” UI are now one application. Previously console.foxglove.dev and studio.foxglove.dev were totally separate apps, now they are combined and live at app.foxglove.dev. In the future we will now be able to show much more context in the visualization view when you’re looking at cloud data.