I currently have the WindowManager.app I am fixing up that draws native decorations with GSTheme on to X11 windows. The screenshot in the gershwin desktop repo shows the result with chromium. I am also working on a Ladybird native GNUstep port where I need to fix the toolbar, rendering issues, and get the codebase in shape for a proper PR. Then I want to start working on fixing up an existing SwiftUI bridge implementation. This would also be a welcome contribution if someone can offer to contribute before I can eventually get to it. If that doesn't happen I would like to create a a native theme for this at some point.