What is the native GUI API for Linux in C++? How is it different from WinAPI?

Hello everyone. I'm a beginner C++ developer transitioning from Windows to Linux. On Windows, I'm used to writing simple windowed applications using WinAPI — it's straightforward: you create a window via CreateWindow, process messages in a loop, and draw buttons and input fields. It's all part of the operating system itself, no third-party libraries needed. Now I'm on Ubuntu and want to write a similar simple program in C++ — a window with a couple of buttons and a text field. But I'm confused: Linux doesn't have a single "native API" for GUI, as I understand. People talk about Xlib, GTK, Qt, but they're not the same thing. Xlib is a low-level protocol for the X Window System, but it doesn't provide ready-made controls (buttons, input fields). GTK and Qt are cross-platform frameworks that are not "native" in the sense