While Fleet is still a JVM app at it's core, it's true that it apparently no longer uses Swing for the UI components. Instead they seem to have reinvented that wheel with their own UI component library called Noria (also JVM) and render it to the screen with Skia (a native 2D graphics library - non JVM).

Pretty fun stuff.

https://blog.jetbrains.com/fleet/2023/02/fleet-below-deck-pa...