Wayland
Modern display server protocol for Linux. Kristian Høgsberg, 2008. Replacement for X11 (X.Org). Default in Fedora, Ubuntu, Pop!_OS since ~2022–2023.
Design philosophy: the compositor is the display server (X11 separated them → lots of architectural pain). Compositors: Mutter (GNOME), KWin (KDE), Sway (i3-like), Hyprland (animations focus, popular on r/unixporn). XWayland is the compat layer for X11 apps. Notorious pains: screen sharing (solved 2024 with PipeWire), screen recording, NVIDIA drivers (solved 2023+). Lives on in embedded + CAD workstations that don't want to switch.