Desku is a free and open-source Java Framework for developing low-code Desktop and Mobile Applications in one codebase.
Get it here: github.com/Osiris-Team/Desku

Your UI code can look as simple as this: vertical().add(text("Hello World!"))

It uses the devices' webview under the hood, meaning your Java UI code gets transformed into HTML/JS/CSS.
For more details about visit the github repo.