What's this camera viewport/clipping visualization for and how do I get rid of it?

Question

In Wireframe and Solid view modes, there's this "cone" of visibility that extends out from one of the cameras and clips all the objects in the scene:

It does not move at all when I switch cameras or move the camera. I've tried clearing the camera border but it had no effect.

It doesn't appear in Material Preview or Rendered modes.

How did this show up, and how can I make it go away?

Answer 1

This might be because you accidentally used the shortcut Alt+B (Viewport clipping?) while trying to define the camera border.

The solution it that case is to press Alt+B once again in 3D viewport mode.