I'm developing a desktop GUI app using Gtk4 at the moment, and I quite like it, including the look/feel of it. The "everything is a widget" approach in Gtk4 makes it much easier to create custom widgets than in past versions, and building on Windows was surprisingly simple (with MSYS2). How does Lazarus compare? I get that it's a whole RAD tool, including IDE, but just in terms of functionality, and ease of extending the components if necessary?