Create an XDG DESKTOP PORTAL Backend for Regolith

Modern sandboxed applications (like Flatpaks) rely on XDG Desktop Portals for essential OS integration, such as screen sharing, opening files, or sending notifications. Tiling window managers often lack a complete and well-maintained xdg-desktop-portal backend, leaving users with a broken experience for many applications. This project will create a working xdg-desktop-portal backend for the Regolith desktop environment. Regolith is a productivity-focused Ubuntu-based desktop environment that combines tiling window managers (Sway, i3) with GNOME components for system management and GUI features. By using xdg-desktop-portal-luminous as a foundation, this project will deliver native portal implementations for complex features like Background and Clipboard, closing a major functionality gap. A key focus of this project is also on upstream contributions. The work will involve implementing the missing Usb portal in the xdg-desktop-portal-gtk backend and helping define and implement a new ScreenCast API version with audio support. This upstream work will directly benefit the entire Linux desktop ecosystem by providing a standard, secure way to capture application audio, a critical feature for apps like Discord and OBS Studio.