It looks like the Win + C shortcut is returning to Windows 11 ... "Choose what happens when you press the Copilot key or Windows logo key + C" — phantomofearth ⛄ (@phantomofearth) March ...

and it's no longer possible to call it up with the Windows+C keyboard shortcut. Only newer keyboards with the dedicated Copilot key will have an easy built-in keyboard shortcut for summoning Copilot.