Comment by account42

LibX11 is still alive and kicking. It is however possible to bundle libX11 and/or libxcb (libX11 today sits on top of libxcb) because the wire protocol between them and the X server is also backwards compatible.

And of course Wayland has XWayland to continue compatibility. This doesn't give you access to new toys but neither does restricting yourself to a 30-year old Win32 API.

And beyond libc/libX11/libxcb, libasound has also provided good backwards compatibility with newer systems implementing shims to make it work. You can also use libpulse directly if you don't care about old/opinionated systems though.