v0.0.27 is a macOS / AppKit release.
That is the supported path. Other platforms are not recommended; wait for a later version.
adwaita
Not recommended on v0.0.27. This version is a macOS / AppKit release. Other platforms exist in the tree; do not ship on them yet. See the manual overview.
Generated bindings for libadwaita 1, produced by cpc-bindgen --gobject from Adw-1.gir. One module: import "adwaita/adwaita" as adw. It sits on gtk4, not a hand-written gtk package.
import "adwaita/adwaita" as adw;
import "gtk4/gtk4" as gtk;
let app: adw::Application = adw::Application::new("org.example.Hello", 0 as u32);
let win: adw::ApplicationWindow = adw::ApplicationWindow::new(app);
Application::new takes (application_id: str, flags: u32). ApplicationWindow::new takes a gtk4::Application. Style manager is app.get_style_manager(); dark appearance is get_dark(). Strings are str via the GObject bridge.
A pure-GTK app that does not want libadwaita should depend on gtk4 only.