Why the changes to the 18.04 desktop?

[Liam Proven]

On Mon, 19 Oct 2020 at 16:49, Paul Smith <paul at mad-scientist.net> wrote:
>
> That means when you press Alt followed by SPACE and C, the computer
> will see a two-key combination: either Alt-SPACE Alt-C or Alt-C
> Alt-SPACE.

You are misreading the OP's description, I presume out of lack of
familiarity with the Microsoft windows-control menu which has been in
Windows since the beginning (~November 1985) and in xNix since the
Motif toolkit and  window manager (July 1989).

The keystroke that opens the window-control menu is Alt+the space bar.
Try it. Even if the button is hidden, as it is by default on GNOME 3
and Unity, it should still work. (But not in non-MS-Windows-like WMs
such as twm or i3.)

Then a menu appears. The contents vary according to WM but the first
few should include:
• "Restore" or "Unmaximize"
• Close
• Resize
• Minimize
• Move
Often then there is a section divider, followed by things like moving
to other virtual desktops, rolling up or unrolling (features borrowed
from Classic MacOS 8/9) and so on.

Normally, each menu option has a hotkey. (KDE does not respect these
and reassigns them. Just one reason I don't like KDE much.)

X is maximize/unmaximize
C is close
R is Restore if it's called that, or Resize if it's called that,
unless it's re_S_ize

It's not very consistent, which is why I personally mainly use
dedicated shortcuts such as Ctrl+W to close a document, Alt+F4 to
close a window, etc.

But they are legitimate keystrokes. Perhaps a better way to write it would be:
Alt+Space, C

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