The jpro.one website looks like it's rendering in the browser to me, are you sure the "standalone" and "cross-platform" options aren't also using a browser render surface?
I also said, "Flutter is about as close as you can get" regarding coming close to what I was referring to.
AppKit is NOT cross-platform. Beyond this, you have other means of embedding a browser-ui application without all of chrome included, see Tauri as one example.
JPro runs the app server side, but the UI is rendered to a stream of commands that are then interpreted by the client in the browser to draw using divs, SVG and browser text. The result is that scrolling, text rendering, fills etc are done by the browser but all the actual app logic is server side. However event handling is all server side. If you run the same app on the desktop then it uses its own rendering stack.
I also said, "Flutter is about as close as you can get" regarding coming close to what I was referring to.
AppKit is NOT cross-platform. Beyond this, you have other means of embedding a browser-ui application without all of chrome included, see Tauri as one example.