OK, tiling window managers are neat and so are TUIs, but web pages are also supposed to work with keyboard only. On Windows, F6 will jump between different panels in an application - give that a try.

The key you’re talking about is the menu key, by the way.

Using a modern OS and the modern web with the keyboard only is essentially a solved problem, not only motivated by efficiency, but also to allow access to people with motor disabilities.

Coming at this from an accessibility… is there any reason the tab, arrow, scape, escape and enter keys would not suffice?

Is it about efficiency? Are Linux GUI apps not expected to be keyboard-only accessible by default?